Detecting loss of user focus in a device

ABSTRACT

A wearable computing device can detect device-raising gestures. For example, onboard motion sensors of the device can detect movement of the device in real time and infer information about the spatial orientation of the device. Based on analysis of signals from the motion sensors, the device can detect a raise gesture, which can be a motion pattern consistent with the user moving the device&#39;s display into his line of sight. In response to detecting a raise gesture, the device can activate its display and/or other components. Detection of a raise gesture can occur in stages, and activation of different components can occur at different stages.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/026,532, filed Jul. 18, 2014, entitled “Raise Gesture Detection in aDevice,” the disclosure of which is incorporated by reference herein inits entirety.

BACKGROUND

The present disclosure relates generally to electronic devices and inparticular to detecting certain categories of gestures made by a userwearing or otherwise operating an electronic device.

Users are increasingly reliant on mobile technology. For instance, manyusers now carry “smart phones” that integrate mobile telephonetechnology with a high-powered computing device, with a form factorsmall enough to allow it to be held in the user's hand during operation.Such devices provide a range of functions including mobile telephony,messaging (e.g., SMS/MMS messaging or similar services), photographyusing a built-in digital camera, email, World Wide Web access, and aseemingly endless array of special-purpose application programs withfunctionality ranging from personal information management (e.g.,calendar, address book, to-do lists) to location-aware navigation andmaps to games. Devices of this kind can put a world of information andentertainment at the user's fingertips.

However, even the smart phone is apparently insufficient to satisfyusers' desire for easy access to information. Wearable technology isattracting considerable interest. It is hoped that with a wearabledevice, a user can enjoy the benefits of mobile technology withincreased convenience.

SUMMARY

One obstacle to widespread adoption of wearable technology is that mostexisting wearable devices are not more convenient to use than a smartphone. For example, wearable devices tend to have a small form factor,which limits the size of battery that can be included in the device.This in turn limits the available operating power. To avoid wastingpower, existing wearable devices generally turn off or power downvarious power-consuming components (e.g., a display) when the user isnot actively engaged with the device.

Because the display and/or user input components are not always on,existing wearable devices generally require some sort of preliminaryuser input, such as touching a button on the wearable device, toindicate that the user wants to engage with the device; this preliminaryinput can trigger the wearable device to activate its display and/orother power-consuming components. This preliminary interaction can makeuse of the device feel unnatural or inconvenient, especially in contrastwith more natural, intuitive interactions familiar from oldertechnology. For example, anyone who has ever worn a wristwatch isfamiliar with the gesture of raising and/or rotating a wrist to checkthe time. For wristwatch-wearers, raising the wrist quickly becomes anatural, automatic motion. But this natural motion only works in aconventional wristwatch because the watch face is “always on,” so thatall the user has to do to see the displayed information (generally thetime) is to bring the watch face into the line of sight. In a moreadvanced electronic device, such as a wearable computing device,however, an always-on display can limit the battery life to the point ofinterfering with ordinary all-day wearing of the device.

Accordingly, it may be desirable for a wrist-wearable computing deviceto detect when a user is raising the wrist on which the device is wornand to automatically activate its display (and/or other components) inresponse to this motion. This can allow the user to obtain visualinformation from the wrist-wearable computing device as easily andintuitively as from a conventional wristwatch.

Certain embodiments of the present invention provide computing devicesthat can detect raise gestures such as wrist-raising gestures. Forexample, a device can include motion sensors such as an accelerometerand/or gyroscope, which can detect movement of the device in real timeand can also infer information about the spatial orientation of thedevice (e.g., by detecting gravitational acceleration acting on thedevice). Based on signals from the motion sensors, algorithms executingon the device can detect a “raise gesture,” which can be defined as amotion pattern indicating that the user is moving or has moved thedevice's display into his line of sight. In response to detecting such agesture, the device can activate its display and/or other components(e.g., a touch screen overlay, speech-processing subsystem, or thelike). In some embodiments, the detection of a raise gesture can occurin stages, and activation of different components can occur at differentstages.

A variety of techniques can be used to detect raise gestures. In someembodiments, the detection algorithms can be heuristically developed andcan take into account both the assumed characteristics of a “focus pose”(which can be an orientation of the wrist-worn computing device thatwould allow the user wearing the device to look at its display) and theparticular starting pose (which can be the orientation of the wrist-worncomputing device prior to being brought into the focus pose). Thus, forexample, a raise gesture can be detected regardless of whether the userbegins from an arm-down position (e.g., when standing or walking) or anarm-lateral position (e.g., when typing). Further, raise-gesturedetection algorithms can be optimized for specific user activities. Forinstance, if a user is running, the natural motion of the user's armsmay create noise in the data collected from a low-power motion sensor(e.g., an accelerometer) that can interfere with detecting a raisegesture. An algorithm optimized for running can incorporate data fromother sensors (e.g., a gyroscopic sensor) to facilitate reliabledetection of a raise gesture, without requiring the user to do anythingdifferent.

In some embodiments, raise-gesture detection algorithms can be executedon a low-power coprocessor (e.g., a motion coprocessor) of the device.Accordingly, when the device is not being actively used, a main orcentral processor (also referred to herein as an applications processor)of the device can be placed into a low-power, or sleep, state to furtherreduce power consumption of the device. Detection of a raise gesture byalgorithms executing on the coprocessor can be used to wake theapplications processor. In some embodiments, a separate “preheat”algorithm can be provided for determining whether to wake theapplications processor, and this algorithm can operate independently ofraise-gesture detection algorithms used to determine whether to activatethe display and/or other user interface components.

Further, after the device enters focus pose, the coprocessor can executealgorithms to determine when the device leaves focus pose, indicatingthat the user has stopped looking at the device. (It should beunderstood that the device state might not always match the ground truthof whether the user is or is not looking the device, although algorithmsdescribed herein can achieve such a match with high, though notnecessarily perfect, reliability.) Detecting that the device has leftfocus pose (also referred to herein as a loss-of-focus event) cantrigger various power-saving measures, such as deactivating the displayand/or other user interface components, allowing the applicationsprocessor to return to sleep state, and so on.

In some embodiments, the coprocessor can execute wake control logic todetermine when to begin or end execution of various algorithms fordetecting raise gestures, loss of focus, and/or preheat events. The wakecontrol logic can also receive notifications of events detected by thevarious algorithms and coordinate corresponding notifications to othercomponents of the device, such as the applications processor and/or userinterface components. For instance, the wake control logic can notifythe applications processor when a raise gesture is detected, and theapplications processor can respond by activating the display and/orother user interface components.

The following detailed description together with the accompanyingdrawings will provide a better understanding of the nature andadvantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D show examples of typical use cases for an embodiment of thepresent invention.

FIG. 2A is a block diagram showing components of a device according toan embodiment of the present invention.

FIG. 2B is a block diagram showing components of a device according toan embodiment of the present invention.

FIG. 3 shows an example of a device-relative coordinate system for awrist-wearable device.

FIG. 4 is flow diagram for a raise-gesture detection process accordingto an embodiment of the present invention.

FIG. 5 is a flow diagram of a process for confirming a raise gestureusing a gesture classifier according to an embodiment of the presentinvention.

FIG. 6 is a state diagram showing states of a raise gesture detectionalgorithm according to an embodiment of the present invention.

FIG. 7 is a functional block diagram of a natural raise gesturedetection module according to an embodiment of the present invention.

FIG. 8 is a flow diagram of another raise-gesture detection processaccording to an embodiment of the present invention.

FIG. 9 is a functional block diagram of a natural raise gesturedetection module according to an embodiment of the present invention.

FIGS. 10A and 10B show an example of a use case for an embodiment of thepresent invention.

FIG. 11 is a flow diagram of a process for detecting a deliberate raisegesture according to an embodiment of the present invention.

FIG. 12 is a functional block diagram of a deliberate raise gesturedetection module according to an embodiment of the present invention.

FIG. 13 is a flow diagram of a process for detecting a loss-of-focusevent according to an embodiment of the present invention.

FIG. 14 is a functional block diagram of a loss-of-focus detectionmodule according to an embodiment of the present invention

FIG. 15 is a flow diagram of a process for determining whether to wakeapplications processor according to an embodiment of the presentinvention.

FIG. 16 is a functional block diagram of a preheat detection moduleaccording to an embodiment of the present invention.

FIG. 17 is a state diagram showing states of wake control logicaccording to an embodiment of the present invention.

FIG. 18 is a flow diagram of a process that can be implemented in wakecontrol logic according to an embodiment of the present invention.

DETAILED DESCRIPTION

Certain embodiments of the present invention can provide a naturalinteraction for users of a device, such as a wrist-wearable device,whose display is not always on. For example, a device can include motionsensors such as an accelerometer and/or gyroscope, which can detectmovement of the device in real time and can also infer information aboutthe spatial orientation of the device (e.g., by detecting gravitationalacceleration acting on the device). Based on signals from the motionsensors, algorithms executing on the wearable computing device candetect a “raise gesture,” which can be defined as a motion patternindicating that the user is moving or has moved the device's displayinto his line of sight. (It is understood that the device state mightnot always match the ground truth of whether the user is or is notlooking the device, although algorithms described herein can achievesuch a match with high, though not necessarily perfect, reliability.)When such a gesture is detected, the wearable computing device canactivate its display. Other components can also be activated based ondetection of a raise gesture, such as user input components (e.g., atouch screen overlay, speech-processing subsystem, or the like). In someembodiments, the detection of a raise gesture can occur in stages, andactivation of different components can occur at different stages.

As used herein, a “wrist-wearable device” (or “wrist-wearable computingdevice”) refers generally to an electronic device that has a form factorsuitable for wearing on the wrist of a user and that can presentinformation to and receive information from the user while being worn onthe user's wrist. In some embodiments, a wrist-wearable device can havea touch-screen display that presents information visually and thatreceives user input in the form of contact gestures made by the user'sfinger (or other tool operated by the user) with the screen orparticular areas on the screen. Other user interface components can beprovided in addition to or instead of a touch-screen display. In someembodiments, a wrist-wearable device can be operated as a standalonedevice (e.g., a device that is not communicating with other devices) oras a companion device to another electronic device with which itcommunicates. For instance, the wrist-wearable device can be paired withthe user's mobile phone or another personal electronic device of theuser, and the wrist-wearable device can leverage or enhancefunctionality of the other device, such as notifying the user ofincoming calls, messages, or other communications.

Wrist-wearable devices can be convenient for users. The device caninterfere minimally or not at all with the user's ordinary activities,and locating the device on the wrist can make it easily accessible. Theuser can simply raise and/or rotate the wrist to bring the device'sdisplay into the user's line of sight. FIGS. 1A and 1B show a typicaluse case, in which a user 100 is wearing a wrist-wearable device 102,which has a display 104. In FIG. 1A, the user's arm 106 is in a naturalposition at the user's side, and display 104 is not in the user's lineof sight. In this position, display 104 can be inactive (e.g., poweredoff or in a low-power state such that information is not visible)without affecting the user experience. In FIG. 1B, user 100 has raisedand rotated arm 106 to a position in which display 104 is now in theuser's line of sight. In this position, it is desirable for display 104to be active (e.g., powered up and illuminated so that the user can viewdisplayed information).

FIGS. 1C and 1D show another typical use case, in which user 100 iswearing wrist-wearable device 102 while engaged in an activity such astyping. In FIG. 1C, the user's arm 106 is positioned for typing onkeyboard 120, with the forearm approximately parallel to the ground andthe wrist slightly pronated to allow the fingers to reach keys. In thisposition, as in FIG. 1A, display 104 can be inactive without affectingthe user experience. In FIG. 1D, user 100 has lifted arm 106 onlyslightly (enough to move the fingers out of contact with keyboard 120)and further pronated the wrist to bring display 104 into the line ofsight. In this position, as in FIG. 1B, it is desirable for display 104to be active.

One option is to have display 104 be active at all times. However,assuming that display 104 consumes more power when active than wheninactive, having display 104 remain active when not in use can createunnecessary drain on a battery that powers device 102. Another option isto activate display 104 only in response to a user input; for instance,the user might press a button on device 102 to wake display 104. This,however, may make device 102 less convenient to use. For instance, asshown in FIGS. 1A and 1B, the user's other hand is holding bag 108,which may make pressing a button on wrist-wearable device 102inconvenient.

In accordance with certain embodiments of the present invention, adevice such as wrist-wearable device 102 can automatically detect whenthe user is preparing to look at the device. Based on such detection,the device can activate its display and/or other power-consumingcomponents. In some embodiments, detection of a user preparing to lookat the device can use motion analysis algorithms executed on a low-powercoprocessor (e.g., a motion coprocessor) within the device. This canallow a main processor (e.g., applications processor) of the device tosleep at least some of the time, further conserving power. In someembodiments, a motion analysis algorithm can detect a category ofmotions (referred to herein as “raise gestures”) associated with a userpreparing to look at a device, such as raising and/or rotating the armand/or wrist (e.g., the difference in arm position between FIGS. 1A and1B or between FIGS. 1C and 1D), and detection of a raise-gesture orrelated motion can trigger various actions, such as activating thedisplay. The raise-gesture-detection algorithms can be sensitive to a“starting” pose of the user, and the particular starting pose may affector alter the expected raise gesture. For instance, the expected raisegesture may be different depending on whether the user's arm isinitially hanging down (as shown in FIG. 1A) or in an elbow-bentposition (e.g., as shown in FIG. 1B). The algorithms can also bemodified to operate in a highly dynamic environment, such as where auser is running, which can affect the type of data that is useful, thestarting pose, and/or the nature of the motion that constitutes theraise gesture.

In instances where a raise gesture can be detected based on naturalmotions associated with looking at the device, a user can naturallyraise and/or rotate the wrist to bring the device's display into theline of sight (e.g., as shown in FIG. 1B or 1D), and immediately (orafter negligible delay) see information displayed without providingexpress input to the device. However, in some situations, detecting sucha “natural” raise gesture may not be practical. Accordingly, a“deliberate” raise gesture can be defined, and detection of thedeliberate raise gesture can result in activating the display and/orother components. The deliberate raise gesture can be defined as aspecific gesture that a user can execute with the intent of activatingthe display of the device; the gesture can be defined based onassumptions about arm or wrist movements that the user would berelatively unlikely to execute when not intending to activate thedisplay. For example, as described below, a deliberate raise gesture canbe defined as corresponding to a double oscillation of the wrist withina short time interval, after which the device stabilizes in a finalpose, other definitions can also be used.

Once the user is determined to be looking at the device-whether viadetection of a natural raise gesture, a deliberate raise gesture, orsome other user interaction with the device—the device's user interfacecan be activated, allowing the user to interact with the device. Forinstance, the user can view information displayed on the device, operateinput controls to provide information and/or instructions to the device,and so on. The user is likely to hold the device in a relativelyconstant orientation while viewing and interacting with it. When theuser is done with the interaction, it is likely that the user's arm willreturn to its starting position or to another position in which thedevice's display is no longer oriented toward the user's line of sight.In some embodiments, a motion that would remove the device form theuser's line of sight can be detected as a “loss-of-focus” gesture andcan trigger various operations to conserve power, such as deactivatingthe display and/or other power-consuming components.

In addition or alternatively, in some embodiments, a main processor ofthe device (also referred to as an “applications processor”) can enter alow-power, or “sleep,” state when the device is not in active use inorder to reduce power consumption. Completing a transition from sleepstate to a “wake” state suitable for active use of the device (alsoreferred to as “waking” the main processor) may have some associatedlatency. Accordingly, it may be desirable to start waking the mainprocessor before the user is actually looking at the device, withoutalso waking the display or other user interface components. Someembodiments provide a “preheat” detection algorithm that can detect theprobable beginning of a raise gesture and initiate waking of the mainprocessor before the raise gesture is completed. This operation canprovide a faster response time where the user does look at the device. Apreheat detection algorithm can operate concurrently with and generallyindependently of a raise-gesture detection algorithm; for instance, thealgorithms can perform different analyses on the same receivedmotion-sensor data.

Detection of raise gestures (including natural and/or deliberate raisegestures) and loss-of-focus gestures can be implemented in a variety ofelectronic devices. FIG. 2A is a block diagram showing components of adevice 200 according to an embodiment of the present invention. Device200 can be, e.g., an implementation of wrist-wearable device 102 ofFIGS. 1A-1D. Device 200 can include a user interface 202, an applicationprocessor 204, a storage subsystem 206, a co-processor 208, anaccelerometer 210, and a gyroscope 212.

User interface 202 can incorporate hardware and software components thatfacilitate user interaction with device 200. Such components can be ofgenerally conventional or other designs. For example, in someembodiments, user interface 202 can include a touch-screen interfacethat incorporates a display (e.g., LED-based, LCD-based, OLED-based, orthe like) with a touch-sensitive overlay (e.g., capacitive or resistive)that can detect contact by a user's finger and/or other objects. Bytouching particular areas of the screen, the user can indicate actionsto be taken, respond to visual prompts from the device, etc. In additionor instead, user interface 202 can include audio components (e.g.,speakers, microphone); buttons; knobs; dials; haptic input or outputdevices; and so on.

Applications processor 204, which can be implemented using one or moreintegrated circuits of generally conventional or other designs (e.g., aprogrammable microcontroller or microprocessor with one or more cores),can be the primary processing subsystem of device 200.

Storage subsystem 206 can be implemented using memory circuits (e.g.,DRAM, SRAM, ROM, flash memory, or the like) or other computer-readablestorage media and can store program instructions for execution byapplications processor 204 as well as data generated by or supplied todevice 200 in the course of its operations. In operation, applicationsprocessor 204 can execute program instructions stored by storagesubsystem 206 to control operation of device 200. For example, processor204 can execute an operating system as well as various applicationprograms specific to particular tasks (e.g., displaying the time,presenting information to the user, obtaining information from the user,communicating with a paired device, etc.). It is to be understood thatapplications processor 204 can execute any processing tasks desired, andembodiments of the present invention can function independently of anyparticular applications.

In embodiments described herein, applications processor 204 can have atleast one “sleep” state in which activity (and power consumption) byapplications processor 204 can be reduced or minimized, and a “wake”state in which applications processor 204 is fully operational. Forexample, applications processor 204 can suspend execution of applicationand/or operating system programs while applications processor 204 is inthe sleep state and resume execution upon reentering the wake state.

Coprocessor 208, like applications processor 204, can be implementedusing one or more integrated circuits of generally conventional or otherdesigns (e.g., a microprocessor and/or microcontroller). Coprocessor 208can execute program code instructions stored as firmware within orotherwise accessible to coprocessor 208, independently of whetherapplications processor 204 is in the sleep or wake state. In someembodiments, coprocessor 208 can have significantly lower powerconsumption during active operation than applications processor 204.

In examples described herein, coprocessor 208 can perform operationsrelated to motion detection and analysis, including detection of raisegestures and/or loss-of-focus gestures. In some embodiments, coprocessor208 can also perform other operations not described herein.

Coprocessor 208 can communicate notifications based on motion analysisto applications processor 204 via an applications processor interface214, which can be a communication interface of conventional or otherdesign (e.g., a communication bus). In some embodiments, thenotifications can include signals that wake applications processor 204from the sleep state and/or that activate user interface 202. In someembodiments, applications processor interface 214 can also deliverunprocessed or partially processed data from accelerometer 210 and/orgyroscope 212 to applications processor 204.

To facilitate motion detection and analysis, coprocessor 208 can receiveinput from on-board motion sensors of device 200, such as accelerometer210 and gyroscopic sensor (also referred to as gyroscope) 212.Accelerometer 210 can be implemented using conventional or other designsand can be sensitive to accelerations experienced by device 200(including gravitational acceleration as well as acceleration due touser motion) along one or more axes. In some embodiments, accelerometer210 can incorporate a 3-axis low-power MEMS accelerometer and canprovide acceleration data at a fixed sampling rate (e.g., 100 Hz).Gyroscope 212 can also be implemented using conventional or otherdesigns and can be sensitive to changes in the orientation of device 200along one or more axes. Gyroscope 212 can also provide orientation dataat a fixed sampling rate (e.g., 100 Hz).

In examples described herein, accelerometer 210 and gyroscope 212 can beoriented within a device to define a device-relative coordinate system.FIG. 3 shows an example of a device-relative coordinate system for awrist-wearable device 300 (which can be, e.g., wrist-wearable device 102of FIGS. 1A-1B). Wrist-wearable device 300 can be secured to a user'swrist 302 by a strap or band 304 such that display 306 can be visible tothe user. As shown, an x axis can be defined substantially parallel tothe user's forearm 308 when the user is wearing device 300, a y axis canbe defined orthogonal to the x axis and in the plane of display 306, anda z axis can be defined orthogonal to the plane of display 306 (pointingtoward the viewer). In some embodiments, an accelerometer can detectacceleration due to gravity as well as motion by the user. For example,if forearm 308 is held horizontally, an accelerometer can detectrotation of a user's wrist (or rotation of wrist-wearable device 300about the x axis) as a change in the y-component of acceleration betweena start time and an end time as the angle of the y axis relative to thedirection of gravity changes. Wrist rotation can also be detected usinga gyroscope as a rotation about the x axis. The coordinate system shownin FIG. 3 is used throughout this disclosure; it is to be understoodthat other coordinate systems can be substituted.

Referring again to FIG. 2A, in some embodiments, coprocessor 208 caninclude various modules that implement operations and algorithms (e.g.,using software or firmware program code) to analyze signals fromaccelerometer 210 and/or gyroscope 212. Some of these modules (referredto variously as “gesture modules” or “gesture-detection modules”) canimplement operations and algorithms pertaining to detection raisegestures and/or loss-of-focus gestures. For example, coprocessor 208 caninclude a “preheat” detection module 220 to detect the possibleinitiation of a raise gesture, a first “main” detection module 222 todetect a natural raise gesture in “low-dynamic” environments, a secondmain detection module 224 to detect a natural raise gesture in“high-dynamic” environments, a “jiggle” detection module 226 to detect adeliberate raise gesture, and a loss-of-focus module 228 to detect whenthe user moves the device out of an assumed line of sight. Examples ofalgorithms that can be implemented in modules 220, 222, 224, 226, and228 are described below.

Wake control logic 230 can control operation of analysis modules 220-228and can receive gesture-state determinations reported by modules220-228. For example, wake control logic can determine, based on thecurrent gesture-state, which of modules 220-228 should be enabled at anygiven time and can selectively enable or disable various algorithms.Selectively disabling an algorithm can reduce power consumption bycoprocessor 208. In addition, based on gesture-state determinations,wake control logic 230 can communicate notifications to applicationsprocessor 204 and/or user interface 202 via application processorinterface 214.

In some embodiments, wake control logic 230 and/or motion analysismodules 220-228 can make use of additional supporting modules that canexecute algorithms or operations selectively or on an ongoing basis. Forexample, activity classifier 232 can receive data from accelerometer 210and/or gyroscope 212 (as well as other sensors, such as physiologicalsensors, that may be present in device 200) and can analyze the data todetermine the type of activity in which the user is engaged, e.g.,walking, sitting or standing still, jogging, running, cycling, riding ina motor vehicle and so on. Activity classifier 232 can implement machinelearning algorithms that identify characteristic features associatedwith various types of activity, and the algorithms can be trained bygathering sensor data during known user activities prior to deployingactivity classifier 232.

In some embodiments, wake control logic 230 can use the output ofactivity classifier 232 to determine whether device 200 is in a“low-dynamic” environment (e.g., sitting, walking, or other relativelyslow movement), in which case low-dynamic main detection module 222 canbe used, or in a “high-dynamic” environment (e.g., running), in whichcase high-dynamic main detection module 224 should be used instead. Wakecontrol logic 230 can selectively enable or disable module 222 or 224depending on the type of environment indicated by activity classifier232.

In some embodiments, gesture classifier 234 can be used to confirmdetection of a natural raise gesture detected by main detection module222 or 224. As described below, main detection modules 222 and 224 cananalyze device position as a function of time to detect a raise gesturein a power-efficient manner. However, these algorithms may sometimesgenerate false positives as a result of user actions that involve amotion similar to raising device 200 into the line of sight but do notactually have that effect. For example, the user may be twisting a doorhandle to open a door or raising a drinking glass to take a drink.Gesture classifier 234 can implement machine learning algorithms thathave been trained to reliably distinguish a raise gesture from othersimilar motions. In some embodiments, gesture classifier 234 can betrained by collecting accelerometer and/or gyroscope data while the userperforms specific actions (including the raise gesture as well as othersimilar actions) in circumstances where the specific action performedcan be recorded along with the accelerometer and/or gyroscope data. Thisinformation can be used to train the algorithm to generate an outputthat reliably discriminates between a raise gesture and other similaractions. Accordingly, when main detection module 222 or 224 detects agesture, the detection algorithm (or wake control logic 230) can providerelevant feature data to gesture classifier 234 for further confirmationor disconfirmation. Examples of the use of gesture classifier 234 aredescribed below in connection with embodiments of main detection module222. In some embodiments, gesture classifier 234 can execute onapplications processor 204 when applications processor 204 is in itswake state.

FIG. 2B is a block diagram showing components of a device 250 accordingto an embodiment of the present invention. Device 250 can be, e.g., animplementation of wrist-wearable device 102 of FIGS. 1A-D. Device 250can include a user interface component 252, an applications processingunit 254, a motion processing unit 258, and a motion sensor 260. Userinterface component 252 can be similar or identical to user interface202 of FIG. 2A (or to components thereof, such as a touch-screendisplay). Main processing unit 254 can be similar or identical toapplications processor 204 of FIG. 2A. Motion sensor 260 can include oneor more motion sensors that can be similar or identical to accelerometer210 and/or gyroscopic sensor 212 of FIG. 2A. Other user interfacecomponents and/or motion sensors can also be used.

Motion processing unit 258 can be similar or identical to co-processor208 of FIG. 2A. Motion processing unit 258 can incorporate variousgesture-detection modules. For instance, preheat detection module 270can be similar or identical to preheat detection module 220 of FIG. 2A.Natural detection module (low dynamic) 272 and natural detection module(high dynamic) 274 can be similar or identical to main detection module(low dynamic) 222 and main detection module (high dynamic) 224 of FIG.2A. Deliberate detection module 276 can be similar or identical tojiggle detection module 226 of FIG. 2A. Loss-of-focus detection module278 can be similar or identical to loss-of-focus detection module 228 ofFIG. 2A. Activity classifier module 282 can be similar or identical toactivity classifier 232 of FIG. 2A. Gesture classifier module 284 can besimilar or identical to gesture classifier 234 of FIG. 2A. Additional ordifferent modules can be included, and some embodiments can include moreor fewer modules than those shown.

It will be appreciated that devices 200 and 250 are illustrative andthat variations and modifications are possible. Embodiments of devices200 or 250 can include other components in addition to or instead ofthose shown. For example, device 200 or 250 can include a power source(e.g., a battery) and power distribution and/or power managementcomponents. Device 200 or 250 can include other sensors, such as acompass, a thermometer or other external temperature sensor, a GlobalPositioning System (GPS) receiver or the like to determine absolutelocation, camera to capture images, physiological sensors (e.g., pulsesensor, blood pressure sensor, skin conductance sensor, skin temperaturesensor), and so on. Device 200 or 250 can include communicationcomponents to enable communication with other devices, includingpersonal devices and/or network-access devices. For example, device 200or 250 can include an RF transceiver and associated protocol stackimplementing one or more wireless communication standards (e.g.,Bluetooth standards; IEEE 802.11 family standards; cellular data networkstandards such as 3G, LTE, etc.) In addition or instead, device 200 or250 can include a wired communication interface such as a receptacleconnector (e.g., supporting USB, UART, Ethernet, or other wiredcommunication protocols).

Further, while devices 200 and 250 are described with reference toparticular blocks, it is to be understood that these blocks are definedfor convenience of description and are not intended to imply aparticular physical arrangement of component parts. Further, the blocksneed not correspond to physically distinct components, and the samephysical components can be used to implement aspects of multiple blocks.Blocks can be configured to perform various operations, e.g., byprogramming a processor or providing appropriate control circuitry, andvarious blocks might or might not be reconfigurable depending on how theinitial configuration is obtained. Embodiments of the present inventioncan be realized in a variety of apparatus including electronic devicesimplemented using any combination of circuitry and software. Further,devices 200 and 250 are fully interchangeable, and it is to beunderstood that any description referencing device 200 (or componentsthereof) can also apply to device 250.

In operation, coprocessor 208 can be “always-on” (e.g., whenever device200 is being worn), and wake control logic 230 can selectively activate(or enable) any or all of modules 220, 222, 224, 226, 228, e.g.,depending on whether the user is looking at the device. These algorithmscan detect and report various gesture-state events including raisegestures, preheat events, loss-of-focus events, etc. Specific examplesare described below. When an algorithm reports an event, wake controllogic 230 can notify applications processor 204 of the event viaapplications processor interface 214. Depending on the event,applications processor 204 can take various actions, such astransitioning from a sleep state to a wake state and/or transitioningcomponents of user interface 202 between active and inactive states.

Examples of specific algorithms to detect gesture-related events willnow be described. As used herein, a “gesture-related event” refersgenerally to any gesture-related transition detected by a module oralgorithm such as modules 220, 222, 224, 226, 228. Examples of suchevents include raise gestures (including identification of“possible,”“detected,” and/or “confirmed” raise gestures as described below),preheat gestures, and/or loss-of-focus gestures. Algorithms of the kinddescribed below can be implemented, e.g., by providing suitable programcode to a programmable processor (e.g., coprocessor 208) and/or byproviding dedicated logic circuitry to perform the operations described.

In some embodiments, a raise gesture detection algorithm can progressthrough a series of states of increasing confidence that a raise gesturehas been performed. For example, an raise-gesture detection algorithmcan select a set of motion-sensor data samples (including accelerometerand/or gyroscopic sensor data) corresponding to a time interval ofinterest (e.g., the amount of time it would likely take a user toexecute a raise gesture). By considering the oldest sample(s) in theset, the algorithm can define a “starting pose,” which can reflect thespatial orientation of the device at the beginning of the time interval.The orientation can be defined relative to an assumed vertical axis ofgravity. Based on the starting pose, the algorithm can determine theamount and/or direction(s) of motion that would likely occur to bringthe device's display into the user's line of sight (also referred to asthe device being brought into a “focus pose”). The likely amount and/ordirection(s) of motion can be expressed as criteria for identifying a“possible” raise gesture, and these criteria can be used to identify,based on some or all of the motion-sensor data samples in the set,whether a possible raise gesture has occurred. The possible raisegesture can be further identified as a “detected” raise gesture bydetermining whether the device, having reached a focus pose, dwells in afocus pose for at least a minimum period of time. A further confirmationcan be performed, if desired, using a gesture classifier. The raisegesture detection algorithm can notify other components of the deviceeach time it identifies a possible, detected, and/or confirmed raisegesture.

By way of specific example of a staged approach to raise-gesturedetection, FIG. 4 is flow diagram for a raise-gesture detection process400 according to an embodiment of the present invention. Process 400 canbe executed, e.g., in main detection (low-dynamic) module 222 of FIG.2A. Raise-gesture detection process 400 can progress through a series ofgesture states (possible, detected, confirmed) and can report each statetransition, e.g., to wake control logic 230 of FIG. 2A. As describedbelow, wake control logic 230 can use the gesture-state transitions todetermine whether and when to wake applications processor 204 and/orwhether and when to instruct applications processor 204 to activate userinterface 202.

Process 400 can start (block 402) when user interface 202 is in aninactive state. At this time, applications processor 204 can be in asleep state or wake state as desired. Accelerometer 210 can be providingupdated data at a regular sampling rate (e.g., 100 Hz), and the data canindicate vector components of acceleration (a_(x), a_(y), a_(z)) usingdevice-relative coordinates as shown in FIG. 3. Received data can bebuffered, e.g., using a circular buffer or FIFO or the like.

At block 404, process 400 can read data samples from the accelerometerdata buffer. The amount of data can depend on the sampling rate anddesired interval of time for analyzing motion. For example, process 400can read data corresponding to a fixed interval, or window, of time,e.g., 0.5 seconds, 1 second, or the like.

At block 406, process 400 can estimate a starting pose for the device,e.g., based on the oldest samples read from the buffer, which cancorrespond to the beginning of the interval. In some embodiments, theaccelerometer readings include gravitational acceleration (1 g, in adirection that depends on the orientation of the device). Accordingly,when other accelerations are relatively small, the orientation of thedevice relative to gravity can be determined based on accelerometerdata. For instance, in the hanging-arm position of FIG. 1A,accelerometer 210 may detect a_(x) of approximately 1 g, and a_(y) anda_(z) of approximately zero. In the typing position of FIG. 1C,accelerometer 210 may detect a_(x) of approximately 0, a_(y) between 0and 1 g, and a_(z) between 0 and −1 g. Thus, block 406 can includecomparing the oldest samples (e.g., average over 5-10 samples) to samplepatterns associated with particular “canonical” starting poses. Thecanonical starting poses can be defined prior to deployment of thedevice, for example, based on accelerometer measurements collected underconditions in which a device-wearer is known to be in a specific pose(e.g., the pose of FIG. 1A or FIG. 1C). In some embodiments, thestarting pose can be defined as a blend of multiple canonical startingposes. For instance, the blend can be defined as a weighted average ofthe canonical starting poses, with the weight for each canonical startpose being based on a measure of the degree of similarity of themeasured device orientation to a device orientation associated with thecanonical starting pose.

At block 408, based on the estimated starting pose, process 400 canselect criteria for identifying a “possible” raise gesture executed fromthat starting pose. Different criteria can be defined for differentstarting poses. For instance, if the starting pose is arm-down (e.g., asshown in FIG. 1A), a raise gesture would be expected to involve liftingthe forearm and rotating the wrist, both of which can be detectedprimarily by reference to changes in a_(x) and a_(y), although someeffect on a may also be expected. If the starting pose is a typing pose(e.g., as shown in FIG. 1C), there might be little or no lifting of theforearm (and consequently little change in a_(x)), but there wouldlikely be a change in tilt, which may be most reliably detectable as achange in a_(y). Other criteria derivable from the accelerometer data inthe buffer can also be employed, such as a parameter quantifyingsmoothness of the motion (assuming that an intentional gesture would beexecuted smoothly, as opposed to accidental jarring or other randommovements a user might experience). In some embodiments, a set ofcriteria for identifying a possible raise gesture given a starting posecan be established heuristically. For instance, a number of users can beasked to make raise gestures from a particular starting pose, and theresulting accelerometer data can be collected throughout the movementfrom starting pose to completion of the raise gesture. Statisticalalgorithms can be applied to analyze this data in order to identifyparticular criteria (e.g., thresholds on change in a_(y), smoothness ofmotion, etc.) for recognizing a possible raise gesture performed fromthat particular starting pose. The criteria at this stage can be coarse,such that some false positives can occur while false negatives are keptrelatively low. The heuristic exercise can be repeated for any number ofcanonical starting poses to establish pose-dependent threshold criteria.In some embodiments, the results of the analysis can be used to generatea table of criteria such that, given a starting pose estimated at block406, a corresponding set of criteria for identifying a possible raisegesture can be selected at block 408 via table lookup. In someembodiments, the starting pose can be defined as a blend of multiplecanonical starting poses, and where this is the case, block 408 caninclude blending selection criteria defined for the multiple canonicalstarting poses.

At block 410, process 400 can determine whether a possible raise gestureis identified, e.g., whether the criteria selected at block 408 aresatisfied. In some embodiments, the determination can include comparingparticular accelerometer data samples and/or other parameters computedfrom the accelerometer data samples to the threshold criteria selectedat block 408, with a possible raise gesture being detected if thethreshold criteria are satisfied. Further, it may be expected that if araise gesture is being performed, upon completion of the gesture, thedevice will come to rest in an orientation consistent with its displaybeing in the user's line of sight. Accordingly, block 410 can includeestimating an ending pose for the device, e.g., based on the newestsamples read from the buffer, which can correspond to the end of theinterval. The ending pose can be compared to a range of poses consistentwith the display being in the user's line of sight (e.g., a range oftilt angles in the y and/or x directions relative to horizontal), with apossible raise gesture being detected if the ending pose is within thisrange. The term “focus pose” is used herein to refer generally to anypose within the range poses deemed consistent with the device being inthe user's line of sight (e.g., based on tilt angles).

If a possible raise gesture is not detected, process 400 can return toblock 404 to read additional accelerometer data. As noted above, thedata read at block 404 can be a fixed-length window that corresponds toa fixed interval of real time. Successive windows of data read duringsuccessive iterations of block 404 can overlap. For instance, if thewindow corresponds to 1 second of real time, successive iterations canhappen every 0.1 second or the like (or at a faster rate; as long as thewindow shifts by at least one sample between iterations, the analysis atsuccessive iterations of blocks 406 and 408 will not be redundant). Thiscan make it less likely that a false negative would occur due towindowing effects.

If, at block 410, a possible raise gesture is detected, then at block412, process 400 can notify wake control logic 230 that a possible raisegesture was detected. As described below, wake control logic 230 cantake action in response to this notification, such as notifyingapplications processor 204 and/or user interface 202. At block 414,process 400 can monitor additional accelerometer data samples (e.g.,including newly received samples outside the original window) to detectwhether the device dwells (e.g., holds an approximately constantposition) in a focus pose or continues to move. For example, as notedabove, focus pose can be defined based on a particular range of tiltangles expected while a user is looking at the device. Tilt angles canbe inferred from accelerometer data, and if the tilt angle reaches andremains within this range, that condition can correspond to dwell in thefocus pose.

In some embodiments, the range of accelerometer data valuescorresponding to focus pose can depend at least in part on the startingpose. For instance, the transition from a starting pose to a focus posecan involve accruing a certain amount of tilt along the y axis (alsoreferred to herein as “y-tilt”). For instance, accrued y-tilt can bemeasured as a net change from a starting a_(y) component that is greaterthan or equal to zero (while the user's wrist is turned away) to anending a_(y) component that is less than zero (when the wrist is turnedto orient the display toward the user's eyes). Block 414 can includemonitoring whether the y-tilt remains constant, continues to accrue, orreverses direction, and a loss of accrued y-tilt can indicate moving outof focus pose.

Process 400 can monitor dwell time at block 414 until the dwell timereaches or exceeds a threshold (e.g., 0.1 seconds, 0.5 seconds, or thelike) or until the accelerometer data indicates that the focus pose hasbeen lost. At block 416, if the focus pose is lost before the dwell timereaches the threshold, process 400 can return to block 404 to determinea new starting pose and attempt to detect another possible raisegesture.

If, at block 416, the dwell time in focus pose exceeds a threshold, apreviously-detected possible raise gesture can be reclassified as adetected raise gesture. At block 418, process 400 can notify wakecontrol logic 230 that a detected raise gesture has occurred. Asdescribed below, wake control logic 230 can take action in response tothis notification, such as activating user interface 202, notifyingapplications processor 204, etc.

In some embodiments, further confirmation of a raise gesture to reducefalse positives may be desired. Accordingly, at block 420, afterdetecting a raise gesture, process 400 can invoke a further analysisprocess, e.g., gesture classifier 234 of FIG. 2A. As described above,gesture classifier 234 can be a machine-learning algorithm that has beenpreviously trained to distinguish a raise gesture from other similargestures. Gesture classifier 234 can analyze data provided by process400 at block 420 to either confirm or disconfirm the detected raisegesture. At block 422, if the raise gesture is confirmed, process 400can so notify wake control logic 230 at block 424, after which process400 can end (block 426). If, at block 422, the raise gesture is notconfirmed, process 400 can so notify wake control logic 230 at block428, after which process 400 can return to block 404 to attempt todetect another possible raise gesture. In some embodiments, after endingat block 426, process 400 can be restarted (at block 402) at any time,e.g., when loss of focus is detected (as described below) or when userinterface 202 becomes inactive for any reason.

FIG. 5 is a flow diagram of a process 500 for confirming a gesture usinga gesture classifier according to an embodiment of the presentinvention. Process 500 can be used in connection with process 400 ofFIG. 4 described above. Process 500 can be executed, e.g., by maingesture detection module 222, which can invoke gesture classifier 234.

Process 500 can begin at block 502, when main gesture detection module222 detects a raise gesture, e.g., at block 416 of process 400. At block504, main gesture detection module 222 can assign a confidence score tothe detected raise gesture. In some embodiments, the confidence scorecan be based on a combination of how well the device pose matchesexpected features of a focus pose (e.g., whether the device pose is nearthe edge or center of the range of accelerometer data values and/or tiltvalues expected for a focus pose) and the length of dwell time in thefocus pose.

At block 506, process 500 can select a salient start point (in time) forthe gesture classifier. The salient start point can be selected based ona trend of accelerometer data samples leading to the focus pose. Forinstance, process 500 can identify the point in time at whichaccelerometer data samples began to change in a manner indicative of theraise gesture. This allows process 500 to account for the fact that auser can execute a raise gesture at different speeds. If the user movedquickly, the salient start point will be closer to the present (i.e.,most recent sample) than if the user moved slowly. Thus, the window ofdata relevant to gesture classification can be variable.

At block 508, process 500 can extract features of interest for thegesture classifier from a window of data extending from the salientstart point to the present. The features of interest for a raise gesturecan depend on how the gesture classifier has been trained. In someembodiments where the gesture classifier operates on accelerometer data,features of interest can include: the actual accelerometer samples(a_(x), a_(y), a_(z)); a smoothness parameter (e.g., based on a standarddeviation of the changes between consecutive accelerometer samples); anaccrued tilt (e.g., y-tilt) as a function of time; and the starting andending device orientation or attitude (e.g., starting and ending tiltvalues). In some embodiments where the gesture classifier operates ongyroscope data, features of interest can include: the actual gyroscopesamples (r_(x), r_(y), r_(z)); an arc length traversed in the horizontalplane (i.e., the plane normal to the direction of gravity); and asmoothness parameter (e.g., based on a standard deviation of the changesbetween consecutive gyroscope samples).

At block 510, process 500 can invoke gesture classifier 234 to processthe extracted features. In some embodiments, gesture classifier 234 canbe a Bayesian classifier that performs a linear discriminant analysis.As described above, the linear discriminant analysis algorithm can betrained in advance of deployment, allowing gesture classifier 234 toquickly compute a probability that the features correspond to a raisegesture. At block 512, process 500 can receive output from gestureclassifier 234. The output can include, for example, a probability(between 0 and 1) that a raise gesture was performed.

At block 514, process 500 can determine whether the raise gesture isconfirmed or not. In some embodiments, the determination can be based ona threshold on the probability output of gesture classifier 234, and thethreshold can be set, e.g., at 0.5, 0.75, 0.85 or some other thresholdas desired. Higher thresholds generally provide fewer false positivesbut more false negatives, and the optimum threshold can be selectedbased on acceptable levels of false positives and/or false negatives ina given implementation. In some embodiments, the threshold can beselected as a function of the confidence score assigned at block 504.For instance, a higher confidence score at block 514 may result in alower threshold on the probability assigned by the gesture classifierwhile a lower confidence score may result in a higher threshold on theprobability assigned by the gesture classifier.

At block 516, process 500 can determine whether to issue a decision orwait for more data. For instance, if the gesture is not confirmed butthe probability output from the gesture classifier is close to thethreshold, it may be preferable to wait for additional data. In thatcase, process 500 can end at block 518 without either confirming ordisconfirming the raise gesture, and control can be returned to block414 of process 400 described above. Alternatively, process 500 can endat block 520 with either a confirmation or disconfirmation, and controlcan be returned to block 422 of process 400 described above.

It will be appreciated that process 500 is illustrative and thatvariations and modifications are possible. Steps described as sequentialmay be executed in parallel, order of steps may be varied, and steps maybe modified, combined, added or omitted. For instance, otherconfirmation algorithms can be used. In some embodiments, process 500can always result in a decision to confirm or disconfirm, without anoption to wait.

In some embodiments, a confirmation or disconfirmation by gestureclassifier 234 can alter device behavior. For example, activation ofsome or all user-interface components can be deferred until a detectedraise gesture is confirmed. As another example, if a user-interfacecomponent is activated in response to a detected raise gesture, asubsequent disconfirmation by gesture classifier 234 can result ininactivating that user-interface component.

FIG. 6 is a state diagram showing gesture states for raise gesturedetection module 222 executing process 400) according to an embodimentof the present invention. Transitions between these states can bereported to wake control logic 230 or otherwise used to affect thestatus of user interface 202 and/or other components of device 200.

State 602 can be a “null” state, in which raise gesture detection module222 has not detected a possible raise gesture. This can be, e.g., theinitial state of process 400 of FIG. 4, and module 222 can remain inthis state until a possible raise gesture is detected (e.g., at block410 of FIG. 4). State 604 can be a “possible gesture” state, in whichmodule 222 has detected a possible raise gesture (e.g., at block 410 ofFIG. 4). If the possible raise gesture is subsequently rejected, module222 can return to null state 602. If the possible raise gesture becomesa detected raise gesture (e.g., at block 416 of FIG. 4), module 222 cantransition to a “detected gesture” state 606. This reflects anincreasing degree of confidence that a raise gesture has occurred. Whilein state 606, further analysis can be performed (e.g., at blocks 420 and422 of process 400) to confirm the detected raise gesture. If thedetected raise gesture is not confirmed, module 222 can return to nullstate 602. If the detected raise gesture is confirmed, then module 222can transition to confirmed gesture state 608. At this point, raisegesture detection is complete, and further execution of module 222 canbe stopped. As noted above, module 222 can be restarted when detecting araise gesture becomes useful again (e.g., when loss of focus is detectedor user interface 202 otherwise becomes inactive). Further, as describedbelow, when confirmed gesture state 608 is reached, other algorithms,such as loss-of-focus detection module 228, can be used to continuemonitoring the gesture state and detect a transition from confirmedgesture state 608 to null state 602. It is to be understood that process400 provides an example of module 222 that provides the states andtransitions of FIG. 6, but other algorithms can be substituted.

FIG. 7 is a functional block diagram of a natural raise gesturedetection module 700 according to an embodiment of the presentinvention. As shown, natural raise gesture detection module 700 can beimplemented in motion processing unit 258 of FIG. 2B, for instance, asnatural raise gesture detection module 272. Natural raise gesturedetection module 700 can also be implemented as main (low dynamic)detection module 222 of FIG. 2A. Natural raise gesture detection module700 can include a starting pose estimation unit 702, a criteriadetermining unit 704, a possible raise gesture determining unit 706, adetected raise gesture determining unit 708, and a confirmation unit710. Each unit can be implemented, for example, using program codeexecutable on a processor and/or dedicated logic circuits.

Starting pose estimation unit 702 can receive motion sensor data andestimate a starting pose based on the motion sensor data. For instance,starting pose estimation unit 702 can implement block 406 of process 400described above. Starting pose estimation unit 702 can provide anestimated starting pose to criteria determining unit 704.

Criteria determining unit 704 can determine criteria for detecting apossible raise gesture based at least in part on the starting poseestimated by starting pose estimation unit 702. For instance, criteriadetermining unit 704 can implement block 408 of process 400 describedabove. Criteria determining unit 704 can provide criteria for detectinga possible raise gesture to possible raise gesture determining unit 706.

Possible raise gesture determining unit 706 can receive motion sensordata and determine whether the received data satisfy the criteriadetermined by criteria determining unit 704. For instance, possibleraise gesture determining unit 706 can implement block 410 of process400 described above. If the criteria are satisfied, possible raisegesture determining unit 706 can notify other system components (e.g.,wake control logic 230 of FIG. 2A or wake control logic module 280 ofFIG. 2B). For instance, possible raise gesture determining unit 706 canimplement block 412 of process 400 described above. Possible raisegesture determining unit 706 can also notify detected raise gesturedetermining unit 708 if the criteria are satisfied.

Detected raise gesture determining unit 708 can receive the notificationof a possible raise gesture from possible raise gesture determining unit706 and can monitor additional accelerometer data to determine whether aminimum dwell time in occurs and/or other conditions are met for adetected raise gesture. For instance, detected raise gesture determiningunit 708 can implement blocks 414 and 416 of process 400 describedabove. If the conditions for a detected raise gesture are met, detectedraise gesture determining unit 708 can notify other system components(e.g., wake control logic 230 of FIG. 2A or wake control logic module280 of FIG. 2B). For instance, detected raise gesture determining unit708 can implement block 418 of process 400. Detected raise gesturedetermining unit 708 can also notify confirmation unit 710 if theconditions for a detected raise gesture are met.

Confirmation unit 710 can perform gesture confirmation based on motionsensor data associated with a detected raise gesture. For instance,confirmation unit 710 can implement blocks 420 and 422 of process 400and/or blocks 504-520 of process 500 described above. In someembodiments, confirmation unit 710 can invoke gesture classifier 234 ofFIG. 2A or gesture classifier module 284 of FIG. 2B. Confirmation unit710 can notify other system components (e.g., wake control logic 230 ofFIG. 2A or wake control logic module 280 of FIG. 2B) as to whether thedetected raise gesture is confirmed or disconfirmed.

It will be appreciated that natural raise gesture detection module 700is illustrative and that variations and modifications are possible. Forinstance, while natural raise gesture detection module 700 is describedwith reference to particular blocks or units, it is to be understoodthat these blocks are defined for convenience of description and are notintended to imply a particular physical arrangement of component parts.Further, the blocks need not correspond to physically distinctcomponents, and the same physical components can be used to implementaspects of multiple blocks. Blocks can be configured to perform variousoperations, e.g., by programming a processor or providing appropriatecontrol circuitry, and various blocks might or might not bereconfigurable depending on how the initial configuration is obtained.Embodiments of the present invention can be realized in a variety ofapparatus including electronic devices implemented using any combinationof circuitry and software.

Another example of an algorithm for detecting a natural raise gesture ishigh-dynamic main detection module 224 of FIG. 2A, which can be adaptedfor detecting natural raise gestures when the user is engaged in ahigh-dynamic activity, such as running. “High-dynamic activity” as usedherein can refer to any activity that inherently involves significantarm or wrist motion such that the accelerometer data can becomeunreliable for detecting a raise gesture. Where the user is engaged in ahigh-dynamic activity, high-dynamic detection module 224 can supplementor replace accelerometer data with data from other sensors, such asgyroscopic sensor 212.

Whether to use low-dynamic detection module 222 or high-dynamicdetection module 224 can be determined, e.g. by wake control logic 230.For example, wake control logic 230 can receive information fromactivity classifier 232 indicating whether the user is currently engagedin a high-dynamic activity (e.g., running) or other activity (e.g.,walking) or no activity. As another example, in some embodiments theuser may provide a direct indication that a high-dynamic activity isabout to begin. For instance, the user may indicate that he is about tobegin running (e.g., by interacting with a workout-tracking applicationprogram on the device), and from this, it can be inferred thathigh-dynamic detection module 222 should be used until the workout ends.Any combination of available input including inputs from activityclassifier 232 and/or direct user input can be used by wake controllogic 230 to infer whether the user is engaged in high-dynamic activity.Responsive to this inference, wake control logic 230 can select eitherlow-dynamic detection module 222 (if the user is not performing ahigh-dynamic activity) or high-dynamic detection module 224. In someembodiments, different algorithms can be provided for use duringdifferent types of activities; for instance there can be multiplehigh-dynamic detection algorithms (e.g., for running versus rowing andso on).

FIG. 8 is a flow diagram of a process 800 for detecting a natural raisegesture during a high-dynamic activity (e.g., running) according to anembodiment of the present invention. Process 800 can be implemented,e.g., in high-dynamic detection module 224 in device 200 of FIG. 2A. Inthis example, high-dynamic detection process 800 can progress through aseries of gesture states (which can be similar or identical to thestates shown in FIG. 6) and can report each state transition, e.g., towake control logic 230 of FIG. 2A. As described below, wake controllogic 230 can use the gesture-state transitions to determine whether andwhen to wake applications processor 204 and/or whether and when toinstruct applications processor 204 to activate user interface 202. Inthis example, process 800 can rely primarily on gyroscope data (e.g.,from gyroscopic sensor 212 of FIG. 2A), supplemented with filteredaccelerometer data (e.g., from accelerometer 210 of FIG. 2A).

Like process 400, process 800 can start (block 802) when user interface202 is in an inactive state. At this time, applications processor 204can be in a sleep state or wake state as desired. Gyroscopic sensor 212can be activated and can provide updated data samples (referred to as“gyroscope data”) at a regular sampling rate (e.g., 100 Hz), and eachgyroscope data sample can indicate components of rotation (r_(x), r_(y),r_(z)) using device-relative coordinates as shown in FIG. 3, with r_(x)denotes rotation about the x axis of FIG. 3 and so on. Receivedgyroscope data can be buffered, e.g., using a circular buffer or FIFO orthe like.

At block 804, process 800 can read data samples from the gyroscope databuffer. The amount of data can depend on the sampling rate, buffer size,and desired interval of time for analyzing motion. For example, process800 can read a fixed-length window of data corresponding to a fixedinterval of real time, e.g., 0.3 seconds, 0.5 seconds, 1 second, or thelike.

At block 806, process 800 can estimate a starting pose for the device.In the context of running, for example, it can be assumed that theuser's arms would be held in a natural bent position with the palmturned inward (toward the user's body). FIGS. 10A and 10B show anexample of a running user wearing wrist-wearable device 102. As shown inFIG. 10A, in a common natural running position, display 104 facesoutward (away from the user's body). The exact angle will vary dependingon the user, and there may be a small oscillatory rotation about the xaxis (as defined in FIG. 3) due to the natural swing of the user's arms.To look at the device while running, the user can pronate the wrist(rotate the palm downward) and perhaps raise the arm, as shown in FIG.10B, to bring display 104 into the line of sight. Such a gestureinvolves a larger rotation about the x axis than the typical arm swingof a runner. Accordingly, accrued rotation about the x axis can be agood first indicator of a possible raise gesture, and at block 808,process 800 can analyze the buffered gyroscope data to determine theaccrued rotation about the x axis.

At block 810, based on the accrued rotation, process 800 can determinewhether a possible raise gesture has been detected. In some embodiments,this determination can also include determining whether rotationalmotion has slowed significantly or stopped at the end of the timeinterval, which would suggest that the user is holding the arm steadyenough to look at the device. If a possible raise gesture is notdetected, process 800 can return to block 804 to read additional data.As noted above, the data read at block 804 can be a fixed-length window.Successive windows of data read on successive iterations of block 804can overlap. For instance, if the window corresponds to 0.5 second ofreal time, successive iterations can happen every 0.1 seconds or thelike (or at a faster rate; as long as the window shifts by at least onesample between iterations, the analysis at successive iterations ofblocks 806 and 808 will not be redundant). Overlapping windows can makeit less likely that a false negative would occur due to windowingeffects.

If, at block 810, a possible raise gesture is detected, then at block812, process 800 can notify wake control logic 230 that a possible raisegesture was detected. In the state diagram of FIG. 6, this cancorrespond to a transition from null state 602 to possible gesture state604. As described below, wake control logic 230 can take action inresponse to this notification, such as notifying applications processor204. At block 814, process 800 can use filtered accelerometer data toconfirm an end pose estimate. The accelerometer data can be heavilyfiltered to remove artifacts of arm motions associated with running andcan be used to confirm that the pose corresponds to one in which thedisplay of the device is likely visible to the user. Based on the endpose estimate, at block 816, process 800 can determine whether toreclassify the possible raise gesture as a detected raise gesture. Ifnot, process 800 can return to block 804 to attempt to detect anotherpossible raise gesture.

If, at block 816, the raise gesture is detected, then at block 818,process 800 can notify wake control logic 230 that a detected raisegesture has occurred. As described below, wake control logic 230 cantake action in response to this notification, such as notifyingapplications processor 204 and/or activating user interface 202. Process800 can end at this state (block 820). Alternatively (not shown in FIG.8), gesture classifier 234 can be used to confirm the detected raisegesture. As described above, gesture classifier 234 can be trained todistinguish natural raise gestures from other similar actions that auser might perform while running (e.g., drinking water from a waterbottle, wiping sweat off forehead), and the results can be similar tothe confirmation portion of process 400 described above.

It will be appreciated that raise-gesture detection processes 400 and800 are illustrative and that variations and modifications are possible.Steps described as sequential may be executed in parallel, order ofsteps may be varied, and steps may be modified, combined, added oromitted. Different thresholds, criteria, and sensor inputs can be used,and different sets of states can be defined as desired. In someembodiments, processes 400 and 800 can be invoked in the alternative,depending on what the user is doing. For example, a gyroscopic sensormay consume more power than an accelerometer. Accordingly, it may bedesirable to power down the gyroscopic sensor and inactivate process 800(which uses gyroscopic sensor data as input) in situations whereaccelerometer data is sufficiently reliable that process 400 can beused, such as where the user is sitting, standing, or walking. Asdescribed above, wake control logic 230 can determine whichgesture-detection algorithm(s) should be active at a given time based oninformation from activity classifier 232 and can activate (or enable)the desired algorithm(s). Other sources of activity information can alsobe used. For instance, in some embodiments, wake control logic 230 canperform a data-quality analysis on received accelerometer data todetermine whether process 400 is likely to be reliable. Process 400 canbe preferred when it is likely to be reliable, and process 800 can beused when process 400 is not likely to be reliable.

FIG. 9 is a functional block diagram of a natural raise gesturedetection module 900 according to an embodiment of the presentinvention. As shown, natural raise gesture detection module 900 can beimplemented in motion processing unit 258 of FIG. 2B, for instance, asnatural raise gesture detection module 274. Natural raise gesturedetection module 900 can also be implemented as main (high dynamic)detection module 224 of FIG. 2A. Natural raise gesture detection module900 can include a starting pose estimation unit 902, a possible raisegesture determining unit 906, and a detected raise gesture determiningunit 908. Each unit can be implemented, for example, using program codeexecutable on a processor and/or dedicated logic circuits.

Starting pose estimation unit 902 can receive motion sensor data andestimate a starting pose based on the motion sensor data. For instance,starting pose estimation unit 902 can implement block 806 of process 800described above. Starting pose estimation unit 902 can provide anestimated starting pose to possible raise gesture determining unit 906.

Possible raise gesture determining unit 906 can receive the estimatedstarting pose and motion sensor data and can determine whether thereceived data satisfy criteria for a possible raise gesture. Forinstance, possible raise gesture determining unit 906 can implementblocks 808 and 810 of process 800 described above. If the criteria aresatisfied, possible raise gesture determining unit 906 can notify othersystem components (e.g., wake control logic 230 of FIG. 2A or wakecontrol logic module 280 of FIG. 2B). For instance, possible raisegesture determining unit 906 can implement block 812 of process 800described above. Possible raise gesture determining unit 906 can alsonotify detected raise gesture determining unit 908 if the criteria aresatisfied.

Detected raise gesture determining unit 908 can receive the notificationof a possible raise gesture from possible raise gesture determining unit906 and can monitor additional motion sensor data to determine whetherconditions are met for a detected raise gesture. For instance, detectedraise gesture determining unit 908 can implement blocks 814 and 816 ofprocess 800 described above. If the conditions for a detected raisegesture are met, detected raise gesture determining unit 908 can notifyother system components (e.g., wake control logic 230 of FIG. 2A or wakecontrol logic module 280 of FIG. 2B). For instance, detected raisegesture determining unit 908 can implement block 818 of process 800.

It will be appreciated that natural raise gesture detection module 900is illustrative and that variations and modifications are possible. Forinstance, while natural raise gesture detection module 900 is describedwith reference to particular blocks or units, it is to be understoodthat these blocks are defined for convenience of description and are notintended to imply a particular physical arrangement of component parts.Further, the blocks need not correspond to physically distinctcomponents, and the same physical components can be used to implementaspects of multiple blocks. Blocks can be configured to perform variousoperations, e.g., by programming a processor or providing appropriatecontrol circuitry, and various blocks might or might not bereconfigurable depending on how the initial configuration is obtained.Embodiments of the present invention can be realized in a variety ofapparatus including electronic devices implemented using any combinationof circuitry and software. Additional blocks can be added (e.g., a blocksimilar to confirmation unit 710 if confirmation is desired).

Used individually or in combination, processes 400 and 800 can detectnatural raise gestures under a variety of conditions. However, it maystill be possible for a user to execute a raise gesture that goesundetected. For example, depending on details of the algorithms, naturalraise gesture detection may be less reliable if the user is lying down(which might violate assumptions about the orientation relative togravity that places the device in the user's line of sight), if the userwears the device such that the display is on the inside of the wrist(which might violate assumptions about the amount and/or direction ofrotation needed to bring the device into the user's line of sight), ifthe user is in an accelerated environment (such as a roller coaster),etc.

Accordingly, some embodiments can provide additional algorithms fordetecting a deliberate raise gesture. This can allow the user toactivate the display by performing a predefined gesture that the userwould be unlikely to perform except when desiring to activate thedisplay. For example, the deliberate raise gesture can be defined as adouble oscillation of the wrist, which “twists” the device back andforth about the x axis (as defined in FIG. 3). The user can perform anoscillation, for example, by quickly rotating the wrist away from anoriginal position and then releasing the rotation so the wrist returnsto the original position. A double oscillation can follow the sequence:rotate; release; rotate; release. Oscillations can be detected asimpulse peaks in motion-sensor data (e.g., accelerometer or gyroscopedata). By requiring a minimum amount of rotation to be accrued and lostduring each oscillation and a maximum time between oscillations, adeliberate raise gesture can be distinguished from most other motions auser might routinely perform (e.g., opening a door or operating ascrewdriver), making it unlikely that the deliberate raise gesture wouldbe detected in cases where the user does not intend to activate thedisplay. Other gestures can be substituted.

FIG. 11 is a flow diagram of a process 1100 for detecting a deliberateraise gesture according to an embodiment of the present invention. Inthis example, the deliberate raise gesture is defined as a “jiggle”gesture in which the user performs a double oscillation of the wrist(rotating the device away from and then toward the line of sight twice)within a short period of time. Process 1100 can be executed, e.g., injiggle detection module 226 of FIG. 2A. In this example, jiggledetection process 1100 can progress from a null state (no gesturedetected) directly to a detected state without an interveningpossible-gesture state. Other states can also be defined if desired.Process 1100 can report the state transition, e.g., to wake controllogic 230 of FIG. 2A. As described below, wake control logic 230 can usethe gesture-state transitions to determine whether and when to wakeapplications processor 204 and/or whether and when to instructapplications processor 204 to activate user interface 202.

Process 1100 can start (block 1102) when user interface 202 is in aninactive state. At this time, applications processor 204 can be in asleep state or wake state as desired. Accelerometer 210 can be providingupdated data at a regular sampling rate (e.g., 100 Hz), and the data canindicate vector components of acceleration (a_(x), a_(x), a_(z)) usingdevice-relative coordinates as shown in FIG. 3. Received data can bebuffered, e.g., using a circular buffer or FIFO or the like.

At block 1104, process 1100 can read data samples from the accelerometerdata buffer. The amount of data can depend on the sampling rate, buffersize, and desired period of time for analyzing motion. For example,process 1100 can read a fixed-length window of data corresponding to afixed interval of real time, e.g., 0.1 seconds, 0.5 seconds, 1 second,or the like.

At block 1106, process 1100 can determine an arm position from theaccelerometer data. Accordingly, block 1106 can include determining anorientation of the device (relative to gravity) based on accelerometerdata, from which an arm position can be inferred.

At block 1108, process 1100 can determine whether the user's arm is“primed” for performing a jiggle gesture. For instance, it may beassumed that a user would only execute a deliberate raise gesture whenthe device is already positioned in the line of sight. As used herein,the user's arm can be considered primed if the device is being heldrelatively still for a short period (e.g., 0.2 seconds, 0.5 seconds, 1.0seconds), suggesting that the user might be trying to look at thedevice. Determining whether the user's arm is primed can includeanalyzing some or all of the data samples in the buffer. For instance,the oldest samples can be analyzed. Additional criteria can also beapplied, such as criteria based on the spatial orientation of thedevice. For instance, if gravitational acceleration is primarily alongthe z axis (as defined in FIG. 3) and there is little or no accelerationalong the x axis, this can suggest that the device display isapproximately parallel to the ground, a common position for a userchecking a wrist-wearable device (or many other devices). Accordingly,additional criteria can be defined based on the direction of gravity.Requiring that a priming criterion be satisfied can reduce falsepositives that might result from incidental movement of the wrist,thereby saving power. In some embodiments, the priming criterion may berelaxed to account for situations where the user's head might not be ina normal vertical orientation (e.g., if the user is lying down),although relaxing the criteria can increase the rate of false positives.In some embodiments, other information may be available to suggestwhether the user's head is vertical or not (e.g., it may be possible todetermine via physiological sensors such as a heart-rate monitor thatthe user is lying down), and such information can be incorporated intothe priming criterion.

If, at block 1108, the arm is not primed, process 1100 can return toblock 1104 to read additional accelerometer data. As noted above, thedata read at block 1104 can be a fixed-length window. Successive windowsof data read during successive iterations of block 1104 can overlap. Forinstance, if the window corresponds to 1 second of real time, successiveiterations can happen every 0.1 second or the like (or at a faster rate;as long as the window shifts by at least one sample between iterations,the analysis at successive iterations of blocks 1106 and 1108 will notbe redundant). This can make it less likely that a false negative wouldoccur due to windowing effects.

If, at block 1108, the user's arm is primed, process 1100 can attempt todetect a jiggle gesture. The jiggle gesture in this example requires twooscillations about the x-axis. Since initiating or stopping a rotationalmotion about the x-axis entails acceleration along the y-axis (see FIG.3), the oscillatory motion of interest in this example can be detectedbased on impulse peaks in the y-component of acceleration. Accordingly,at block 1110, process 1100 can analyze the accelerometer data to detectsuch a peak. In some embodiments, a peak or spike in the y-component ofjerk (time derivative of acceleration) can be used to detect theoscillation. Given that the gesture to be detected is intentional, thepeak is expected to stand out against any background of sample-to-samplevariation due to random motions that may be occurring (e.g., due to theuser walking, riding in a vehicle, jogging, etc.). Accordingly, thecriteria for detecting a twist or oscillation can be defined relative toa background of sample-to-sample variations measured at around the sametime. Particular criteria for peak detection can be definedheuristically, e.g., by having a number of users perform the jigglegesture and analyzing the accelerometer data to identify specificthresholds on acceleration and/or jerk. The thresholds can be definedbased on absolute values or values relative to the current level ofbackground variation.

At block 1112, if a first peak is not detected, process 1100 can returnto block 1104 to continue monitoring accelerometer data. If a first peakis detected, then at block 1114, process 1100 can attempt to detect asecond peak. In this example, the second peak should be in the samedirection as the first, indicating that the user repeated theoscillatory motion, and the criteria can be the same as or similar tothose used at block 1112.

If, at block 1116, a second peak is not detected, then at block 1118,process 1100 can determine whether a timeout period has elapsed sincedetecting the first peak at block 1112. The timeout period can be usedto distinguish a deliberate jiggle gesture from other wrist-rotationmotions and can be selected based on measurement of the time requiredfor various individuals to intentionally execute a double oscillation.For instance, the timeout period can be 0.2 seconds, 0.5 seconds, or thelike.

Process 1100 can continue to search for the second peak until a secondpeak is detected or the timeout period expires. If, at block 1118, thetimeout period expires, process 1100 can return to block 1104 to collectadditional accelerometer data and again search for two peaks.

If, at block 1116, a second peak is detected, then at block 1120,process 1100 can analyze additional accelerometer data to determinewhether the position of the device has stabilized. If, at block 1122,the position has not stabilized, this can indicate that the oscillationoccurred for some other reason not related to looking at the device, andprocess 1100 can return to block 1104 to collect additionalaccelerometer data and again search for two peaks.

If, at block 1122, the position has stabilized, this can correspond todetecting the jiggle gesture, and at block 1124, process 1100 can notifywake control logic 230 that the jiggle gesture has been detected. Asdescribed below, wake control logic 230 can take action in response tothis notification, such as activating user interface 202 and/or wakingapplications processor 204.

It will be appreciated that process 1100 is illustrative and thatvariations and modifications are possible. Steps described as sequentialmay be executed in parallel, order of steps may be varied, and steps maybe modified, combined, added or omitted. Different thresholds, criteria,and sensor inputs can be used, and different sets of states can bedefined as desired. In some embodiments, detection of the first peak canbe reported as a possible raise gesture, or detection of two peaks canbe reported as a possible raise gesture prior to determining whether thedevice position has stabilized. Other deliberate raise gestures can bedetected by defining different criteria (e.g., more or fewer impulsepeaks, accelerations in different directions, etc.). In someembodiments, process 1100 can be executed concurrently with eitherprocess 400 or process 800, so that the user can activate the display atany time when it is inactive by performing either a natural ordeliberate raise gesture.

FIG. 12 is a functional block diagram of a deliberate raise gesturedetection module 1200 according to an embodiment of the presentinvention. As shown, deliberate raise gesture detection module 1200 canbe implemented in motion processing unit 258 of FIG. 2B, for instance,as deliberate raise gesture detection module 276. Natural raise gesturedetection module 700 can also be implemented as jiggle detection module226 of FIG. 2A. Deliberate raise gesture detection module 1200 caninclude a priming detection unit 1202, an impulse peak detecting unit1204, and a stability detection unit 1206. Each unit can be implemented,for example, using program code executable on a processor and/ordedicated logic circuits.

Priming detection unit 1202 can receive motion sensor data and determinefrom the data whether the user's arm is primed to execute a deliberateraise gesture. For instance, priming detection unit 1202 can implementblocks 1106 and 1108 of process 1100 described above. When primingdetection unit 1202 determines that the user's arm is primed, primingdetection unit 1202 can provide a notification to impulse peak detectionunit 1204.

Impulse peak detection unit 1204 can receive additional motion sensordata and detect the presence of a target number (e.g., one, two, orthree) of impulse peaks based on the data. For instance, impulse peakdetection unit 1204 can implement blocks 1110-1118 of process 1100described above. When the number of impulse peaks indicative of a raisegesture (e.g., two in the example above) has been detected, impulse peakdetection unit 1204 can provide a notification to stability detectionunit 1206.

Stability detection unit 1206 can receive additional motion sensor dataand determine whether the data indicates that the device position hasstabilized following the detected impulse peak(s). For instance,stability detection unit 1206 can implement blocks 1120 and 1122 ofprocess 1100 described above. If stability is detected, stabilitydetection unit 1206 can notify other system components (e.g., wakecontrol logic 230 of FIG. 2A or wake control logic module 280 of FIG.2B). For instance, stability detection unit 1206 can implement block1124 of process 1100 described above.

It will be appreciated that deliberate raise gesture detection module1200 is illustrative and that variations and modifications are possible.For instance, while deliberate raise gesture detection module 1200 isdescribed with reference to particular blocks or units, it is to beunderstood that these blocks are defined for convenience of descriptionand are not intended to imply a particular physical arrangement ofcomponent parts. Further, the blocks need not correspond to physicallydistinct components, and the same physical components can be used toimplement aspects of multiple blocks. Blocks can be configured toperform various operations, e.g., by programming a processor orproviding appropriate control circuitry, and various blocks might ormight not be reconfigurable depending on how the initial configurationis obtained. Embodiments of the present invention can be realized in avariety of apparatus including electronic devices implemented using anycombination of circuitry and software.

Once a raise gesture (natural or deliberate) has been detected, it canbe assumed that the user is now focused on the device and may beinteracting with it. Any type of user interaction can be supported, andthe duration of interaction can be as long as the user desires. It isexpected that at some point, the interaction will end. When theinteraction ends, it may be desirable to return the display to itsinactive state in order to conserve power.

In some embodiments, a user can expressly indicate the end of aninteraction, e.g., by pressing a button on the device to inactivate thedisplay. In addition or instead, a device can infer that the interactionhas ended based on lack of user input over a sufficiently long period oftime, although such an inference might not be accurate if the user isstill looking at presented information. Accordingly, in someembodiments, a device can automatically detect when the user loses focuson the device, based on motion-sensor data. For example, if the usermoves the device's display out of the line of sight, this can indicatethat the user has lost focus. Such motion is referred to herein as a“loss-of-focus gesture.”

Automatic detection of loss-of-focus gestures (also referred to hereinas “loss-of-focus events”) can be facilitated using motion-basedalgorithms. FIG. 13 is a flow diagram of a process 1300 for detecting aloss-of-focus event according to an embodiment of the present invention.Process 1300 can be executed, e.g., in loss-of-focus detection module228 of FIG. 2A. In this example, process 1300 can be performed while thedevice is in a focus state (e.g., after detecting and/or confirming araise gesture using any of processes 400, 800, or 1100 described above).Loss of focus can be detected based on changes in tilt angle or rotationof the device, particularly changes in y-tilt. Process 1300 can report adetected loss-of-focus event, e.g., to wake control logic 230 of FIG.2A. As described below, wake control logic 230 can use the reportedevent to determine whether to inactivate user interface 202.

Process 1300 can start (block 1302) when user interface 202 is in anactive state. The active state can be achieved as a result of any of thegesture-detection processes described above, as a result of othergesture-detection processes, or in response to a manual indication fromthe user (e.g., touching a button on device 200). At this time,applications processor 200 can also be in a wake state. Accelerometer210 can be providing updated data at a regular sampling rate (e.g., 100Hz), and the data can indicate vector components of acceleration (a_(x),a_(y), a_(z)) using device-relative coordinates as shown in FIG. 3.Received data can be buffered, e.g., using a circular buffer or FIFO orthe like.

At block 1304, process 1300 can read data samples from the accelerometerdata buffer. The amount of data can depend on the sampling rate, buffersize, and desired period of time for analyzing motion. For example,process 400 can read a fixed-length window of data corresponding to afixed interval of real time, e.g., 0.5 seconds, 1 second, or the like.

At block 1306, process 1300 can determine an initial tilt, e.g., basedon the measured x-component and/or y-component of acceleration orrotation angles for samples near the beginning of the buffer. Duringtime periods when the user is holding the device in the line of sight,it is expected that tilt (or at least y-tilt) will remain approximatelyconstant, and when process 1300 starts, a reference tilt can be defined.In some embodiments, automatically detecting a raise gesture can includedetecting accrual of tilt (e.g., y-tilt), and the initial tilt orreference tilt can be defined based on the accrued tilt that wasdetected at block 1306.

At block 1308, process 1300 can detect a change in tilt, e.g., relativeto the initial tilt or reference tilt. In some embodiments, the changecan be ignored unless the change is in a direction that would move thedisplay away from the user's line of sight. For instance, a user lookingat device 300 of FIG. 3 may tend to hold his arm such that device 300 isparallel to the ground or tilted such that gravitational accelerationwould impart a negative acceleration component along the y axis. Achange from zero or negative a_(y) to positive a_(y) can suggest thatthe user has rotated device 300 out of the line of sight. In someembodiments, automatically detecting a raise gesture can includedetecting accrual of tilt (e.g., as described above with reference toFIG. 4), and block 1308 can include detecting a negation of the accruedtilt (e.g., y-tilt), indicating that the user is returning the device toits unraised position.

If, at block 1310, a sufficiently large change in tilt has beendetected, then at block 1312, process 1300 can notify wake control logic230 that a loss-of-focus event has been detected. As described below,wake control logic 230 can take action in response to this notification,such as inactivating user interface 202 and/or notifying applicationsprocessor 204.

If, at block 1310 a large change in tilt is not detected, then at block1314, process 1300 can estimate an arm position for the user based onthe accelerometer data. For instance, it is possible that the user couldlower the arm without rotating the wrist. Arm position can be estimatedbased on accelerometer data and assumptions about how the user iswearing the device, as described above. At block 1316, process 1300 candetermine whether the user's arm has been lowered. For example, in thecoordinate system of FIG. 3, a lowered arm can be detected based ongravitational acceleration aligning approximately with the x-axis. Insome embodiments, block 1316 can include comparing starting and endingarm positions to detect a change indicative of the user moving the armto a lowered position. If arm lowering is detected, then at block 1312,process 1300 can notify wake control logic 230 of a loss-of-focus event.Once a loss-of-focus event is detected, process 1300 can end.

It will be appreciated that process 1300 is illustrative and thatvariations and modifications are possible. Steps described as sequentialmay be executed in parallel, order of steps may be varied, and steps maybe modified, combined, added or omitted. Different thresholds, criteria,and sensor inputs can be used; for instance, gyroscope data can be usedin addition to or instead of accelerometer data. In some embodiments,the sensors to be used (e.g., accelerometer and/or gyroscope) can beselected dynamically based on the user's current activity as reported byactivity classifier 232. For example, if the user is running, gyroscopedata may be more reliable; if the user is sitting still, it may be morepower-efficient to use accelerometer data and power down gyroscopicsensor 212. In addition, the criteria for detecting loss-of-focus can bevaried based on the user's current activity. For instance, the criteriamay be modified to make loss of focus less likely to be detected whilethe user is running, since the arm would be expected to be less steady.

Further, in some embodiments, it may be desirable to avoid a falseloss-of-focus detection due to transitory motions. Accordingly,loss-of-focus detection can incorporate hysteresis, such that loss offocus is not detected until the device goes out of the focus pose andremains there for some minimum time period. If the device re-entersfocus pose before the time expires, the loss-of-focus detectionalgorithm can reset. The minimum time period can depend on how long thedevice has been in the focus pose, with a longer dwell time in focuspose correlating with a longer required time out of focus to trigger aloss-of-focus event. It should be noted that delayed detection of aloss-of-focus event (and deactivating the display) is expected to beless disruptive to the user than prematurely detecting a loss-of-focusevent (and deactivating the display) when the user is, in fact, stilllooking at the display. Accordingly, the loss-of-focus algorithm can betuned to err on the side of being slow to detect loss of focus.

FIG. 14 is a functional block diagram of a loss-of-focus detectionmodule 1400 according to an embodiment of the present invention. Asshown, loss-of-focus detection module 1400 can be implemented in motionprocessing unit 258 of FIG. 2B, for instance, as loss-of-focus detectionmodule 278. Loss-of-focus detection module 1400 can also be implementedas loss-of-focus detection module 228 of FIG. 2A. Loss-of-focusdetection module 1400 can include an orientation determining unit 1402,an orientation change detection unit 1404, an arm position estimationunit 1406, and a focus determination unit 1408. Each unit can beimplemented, for example, using program code executable on a processorand/or dedicated logic circuits.

Orientation determining unit 1402 can receive motion sensor data anddetermine from the data an orientation for the device. For instance,orientation determining unit 1402 can implement block 1306 of process1300 described above, with the orientation being characterized by tilt(which can be determined from accelerometer data, gyroscope rotationangles, or the like). Orientation determining unit 1402 can provide thedetermined orientation to orientation change detection unit 1404.

Orientation change detection unit 1404 can determine, e.g., based ondata received over time from orientation determining unit 1402, whethera change in orientation has occurred. For instance, orientation changedetection unit 1404 can implement block 1308 of process 1300 describedabove. Orientation change detection unit 1404 can provide orientationchange information (e.g., a quantitative measurement of the change) tofocus determination unit 1408.

Arm position estimation unit 1406 can receive motion sensor data anddetermine from the data an estimated arm position of an arm on which thedevice is presumed to be worn. For instance, arm position estimationunit 1406 can implement block 1314 of process 1300 described above. Armposition estimation unit 1406 can provide information about the armposition (e.g., an estimated arm position or a change in arm position)to focus determination unit 1408.

Focus determination unit 1408 can receive orientation change informationfrom orientation change detection unit 1404 and arm position informationfrom arm position estimation unit 1406. Based on the receivedinformation, focus determination unit 1408 can determine whether loss offocus has occurred. For instance, focus determination unit 1408 canimplement blocks 1310 and/or 1316 of process 1300 described above. Whenfocus determination unit 1408 determines that loss of focus hasoccurred, focus determination unit 1408 can notify other systemcomponents (e.g., wake control logic 230 of FIG. 2A or wake controllogic module 280 of FIG. 2B). For instance, focus determination unit1408 can implement block 1312 of process 1300 described above.

It will be appreciated that loss of focus detection module 1400 isillustrative and that variations and modifications are possible. Forinstance, while loss of focus detection module 1400 is described withreference to particular blocks or units, it is to be understood thatthese blocks are defined for convenience of description and are notintended to imply a particular physical arrangement of component parts.Further, the blocks need not correspond to physically distinctcomponents, and the same physical components can be used to implementaspects of multiple blocks. Blocks can be configured to perform variousoperations, e.g., by programming a processor or providing appropriatecontrol circuitry, and various blocks might or might not bereconfigurable depending on how the initial configuration is obtained.Embodiments of the present invention can be realized in a variety ofapparatus including electronic devices implemented using any combinationof circuitry and software.

Used together, processes and modules such as those described above canallow a device to detect when the user starts looking at the device andstops looking at the device. The user interface can be activated orinactivated depending on whether the user is currently looking or not.In some embodiments, the same or similar processes can be used to wakeapplications processor 204 and/or other components of the device from alow-power (sleep) state, in preparation for user interaction. However,depending on implementation, waking applications processor 204 may havea longer latency than activating user interface 202, and havingapplications processor 204 awake for a given period of time may consumeless power than having user interface 202 active. Accordingly, it may bedesirable to start waking applications processor 204 (without alsoactivating user interface 202) at an earlier stage rather than waitingfor a raise gesture to be detected or confirmed as described above.

FIG. 15 is a flow diagram of a process 1500 for determining whether towake applications processor 204 according to an embodiment of thepresent invention. Process 1500 can be executed, e.g., in preheatdetection module 220 of FIG. 2A. In this example, process 1500 candetect a sequence of accelerometer samples consistent with early stagesof a natural (or deliberate) raise gesture and can notify wake controllogic 230 when such a sequence is detected.

Process 1500 can operate concurrently with but independently of othergesture detection algorithms (e.g., processes 400, 800, 1100 describedabove). For instance, process 1500 can be used to determine whether towake applications processor 204 while a different algorithm (e.g.,process 400 or process 800) is used to determine whether to activateuser interface 202.

Process 1500 can start (block 1502) when applications processor 204 isin its sleep state. Accelerometer 210 can be providing updated data at aregular sampling rate (e.g., 100 Hz), and the data can indicate vectorcomponents of acceleration (a_(r), a_(y), a_(L)) using device-relativecoordinates as shown in FIG. 3. Received data can be buffered, e.g.,using a circular buffer or FIFO or the like.

At block 1504, process 1500 can evaluate a most recent accelerometersample (or a short window of samples) to determine a current pose. Atblock 1506, process 1500 can determine whether the samples satisfy acondition indicative of a possible start of a raise gesture. In someembodiments, the determination can depend on a change in measuredacceleration between consecutive samples. For instance, as the userrotates the wrist to bring the device into the line of sight, one canexpect the a_(y) component to decrease from a zero or positive (due togravity) starting state. In addition, if the user's arm is initiallydown, the a_(x) component may also change from positive (due to gravity)toward zero as the user raises his arm. Accordingly, the condition atblock 1506 can depend on a weighted sum of change in a_(x) and change ina_(y) between consecutive samples, with the a_(y) component being givengreater weight. In some embodiments, the condition can depend on thestarting pose (e.g., the relative weight of a_(x) can be larger for anarm-down starting pose than for an arm-horizontal starting pose).Process 1500 can continue to monitor accelerometer data until a possibleinitiation of a raise gesture is detected at block 1506. For instance,blocks 1504 and 1506 can be performed for each new accelerometer datasample as it is received.

Once a possible initiation of a raise gesture is detected at block 1506,process 1500 can monitor subsequent samples to determine whether theraise gesture continues to progress. For instance, at block 1508,process 1500 can initialize two counters, referred to as N_(NO) andN_(YES). The counters can be initialized, e.g., to zero. At block 1510,process 1500 can evaluate the next accelerometer sample, and at block1512, process 1500 can determine whether the sample is or is notconsistent with a raise gesture in progress. The determination can bebased on various criteria such as whether the change in device position(e.g., tilt and arm angle) is consistent with continuing a raisegesture, smoothness of the motion (on the assumption that a randommotion will not be as smooth as a raise gesture), and so on. In someembodiments, the criteria can depend on the start pose. For instance,from an arm-down starting pose (e.g., as in FIG. 1A), a larger change ina_(x) would be expected than if the forearm is initially horizontal(e.g., as in FIG. 1C). Accordingly, the decision can incorporate thecurrent accelerometer sample as well as a device trajectory inferredfrom previous samples.

If, at block 1512, the next sample is consistent with the gesture, thenat block 1514, counter N_(YES) can be incremented. At block 1516,N_(YES) can be compared to a threshold “MinYes” (e.g., ten samples,eleven samples, fourteen samples or the like) to determine whetherenough samples consistent with a raise gesture have been detected. IfN_(YES) has reached the threshold MinYes, then at block 1518, process1500 can notify wake logic 230 of a preheat event (also referred toherein as a “preheat gesture”). In response, wake logic 230 can, forexample, wake applications processor 204. In this embodiment, a preheatevent does not result in activating user interface 202, and the userneed not know when or whether preheat events occur. If the threshold isnot exceeded at block 1516, process 1500 can return to block 1510 tocontinue to accumulate and evaluate accelerometer data samples.

If, at block 1512, the next accelerometer data sample is not consistentwith a raise gesture, then at block 1520, counter N_(NO) can beincremented. At block 1522, N_(NO) can be compared to a threshold“MaxNo” (e.g., two samples, four samples, five samples, or the like) todetermine whether too many samples inconsistent with a raise gesturehave been detected. If N_(NO) reaches the threshold MaxNo, then at block1524, process 1500 can reset, returning to block 1504 to look for a newpossible beginning of a raise gesture.

In this manner, whether process 1500 detects a preheat event can dependon whether threshold MinYes is reached before threshold MaxNo isreached. For example, in one embodiment, threshold MinYes can be set to11 and threshold MaxNo can be set to 5. If, after a possible initiationof a raise gesture is detected at block 1506, eleven samples consistentwith the gesture are received before five samples inconsistent with thegesture are received, process 1500 will generate a preheat event. Ifeleven samples consistent with the gesture are not received before fivesamples inconsistent with the gesture are received, then process 1500will not generate a preheat event and will instead return to block 1504to, in effect, start over. If new samples are received at 100 Hz, thenprocess 1500 can detect initiation of a raise gesture within 150 msafter its beginning.

It will be appreciated that process 1500 is illustrative and thatvariations and modifications are possible. Steps described as sequentialmay be executed in parallel, order of steps may be varied, and steps maybe modified, combined, added or omitted. For instance, sampling ratesand decision criteria can be varied. The sensitivity of the preheatdetection can be tuned depending on how much time is required for theapplications processor to transition from sleep state to wake state. Thepreheat event can be detected early enough that, by the time the usercompletes the raise gesture, the applications processor is in the wakestate and ready to process user input. In some embodiments, earlydetection of preheat and waking of the applications processor can helpto reduce or eliminate user-perceptible delay in the device's responseto a natural raise gesture. Earlier detection may result in more falsepositives, and the sensitivity can be tuned such that a preheat event isdetected as late in the gesture as possible while still allowingsufficient time for the applications processor to transition to the wakestate.

In some embodiments, a specific algorithm to detect loss of preheat isnot implemented. For example, applications processor 204 canautomatically revert to the sleep state if no user input, raise-gesturedetection or other activity indicating that the user is interacting withdevice 200 occurs within a certain time interval after waking.Alternatively, wake control logic 230 can notify applications processor204 if a possible raise gesture is not received within a certain timeinterval after a preheat event, and applications processor 204 can usethis information to determine whether to revert to sleep state. Someembodiments can provide a loss-of-preheat algorithm, e.g., detectingwhether received samples continue to be consistent with a raise gestureand indicating loss of preheat if they do not continue to be consistentwith a raise gesture or if the preheat event is not followed by adetected raise gesture within a specified time period.

FIG. 16 is a functional block diagram of a preheat detection module 1600according to an embodiment of the present invention. As shown, preheatdetection module 1600 can be implemented in motion processing unit 258of FIG. 2B, for instance, as preheat detection module 270. Preheatdetection module 1600 can also be implemented as preheat detectionmodule 220 of FIG. 2A. Preheat detection module 1600 can include apossible gesture start determination unit 1602, a sample evaluation unit1604, a counter unit 1606, and a preheat determination unit 1608. Eachunit can be implemented, for example, using program code executable on aprocessor and/or dedicated logic circuits.

Possible gesture start determination unit 1602 can receive motion sensordata samples and determine from the data samples whether a possiblegesture start has occurred. For instance, possible gesture startdetermination unit 1602 can implement block 1504 of process 1500described above. When a possible gesture start is determined to haveoccurred, possible gesture start determination unit can notify sampleevaluation unit 1604 and counter unit 1606.

Sample evaluation unit 1604 can receive motion sensor data samples andevaluate each sample as it is received to determine whether it isconsistent or inconsistent with a continuation of a possible raisegesture. For instance, sample evaluation unit 1604 can implement blocks1510 and 1512 of process 1500 described above. Sample evaluation unit1604 can provide, to counter unit 1606, a decision output indicatingwhether the sample is consistent or inconsistent with a continuation ofa possible raise gesture.

Counter unit 1606 can maintain a first counter to count samples that aredetermined by sample evaluation unit 1604 to be consistent with acontinuation of a possible raise gesture and a second counter to countsamples that are determined by sample evaluation unit 1604 to beinconsistent with a continuation of a possible raise gesture. Thesecounters can correspond to the N_(YES) and N_(NO) counters describedabove. Counter unit 1606 can initialize the two counters (e.g., to zero)in response to being notified of a possible gesture start by possiblegesture start determination unit 1602. For instance, counter unit 1606can implement block 1508 of process 1500 described above. Afterinitializing the two counters, counter unit 1606 can increment one ofthe two counters in response to each decision output received fromsample evaluation unit 1604, with the first counter being incremented ifthe decision output indicates that the sample is consistent with acontinuation of a possible raise gesture and the second counter beingincremented if the decision output indicates that the sample isinconsistent with a continuation of a possible raise gesture. Forinstance, counter unit 1606 can implement blocks 1540 and 1520 ofprocess 1500 described above. Counter unit 1606 can provide the firstand second counter values to preheat determination unit 1608.

Preheat determination unit 1608 can receive the first and second countervalues from counter unit 1606 and can determine whether either a preheatevent or a reset event has occurred. For instance, preheat determinationunit 1608 can implement blocks 1516 and 1522 of process 1500 describedabove. If a preheat event has occurred (e.g., if the first counter hasexceeded the value MinYes as described above), preheat determinationunit 1608 can notify other system components (e.g., wake control logic230 of FIG. 2A or wake control logic module 280 of FIG. 2B). Forinstance, preheat determination unit 1608 can implement block 1518 ofprocess 1500 described above. If a reset event has occurred (e.g., ifthe second counter has exceeded the value MaxNo as described above),preheat determination unit 1608 can notify possible gesture startdetermination unit 1602, and possible gesture start determination unit1602 can begin again to determine whether a possible gesture start hasoccurred. In addition, preheat determination unit 1608 can also notifysample evaluation unit 1604 and/or counter unit 1606 of a preheat orreset event, and the notified units can respond accordingly; forinstance, sample evaluation unit 1604 can stop evaluating samples aftereither a preheat or reset event, until such time as a next possiblegesture start occurs. It should be understood that not every sampleevaluated by sample evaluation unit 1604 needs to result in either apreheat or reset event, as it may take several samples for one or theother counter to reach the relevant threshold.

It will be appreciated that preheat detection module 1600 isillustrative and that variations and modifications are possible. Forinstance, while preheat detection module 1600 is described withreference to particular blocks or units, it is to be understood thatthese blocks are defined for convenience of description and are notintended to imply a particular physical arrangement of component parts.Further, the blocks need not correspond to physically distinctcomponents, and the same physical components can be used to implementaspects of multiple blocks. Blocks can be configured to perform variousoperations, e.g., by programming a processor or providing appropriatecontrol circuitry, and various blocks might or might not bereconfigurable depending on how the initial configuration is obtained.Embodiments of the present invention can be realized in a variety ofapparatus including electronic devices implemented using any combinationof circuitry and software.

Using the various gesture detection modules and/or processes describedabove, wake control logic 230 of FIG. 2A (or wake control logic module280 of FIG. 2B) can implement state machine behavior as shown in FIG.17, which is a state diagram showing states of wake control logic 230according to an embodiment of the present invention. Transitions betweenstates can occur in response to notifications from preheat detectionmodule 220 (e.g., executing process 1500), low-dynamic main detectionmodule 222 (e.g., process 400), high-dynamic main detection module 224(e.g., process 800), jiggle detection module 226 (e.g., process 1100),and loss-of-focus detection module 228 (e.g., process 1300).

State 1702 can be a “null” state, in which device 200 is idle, withapplications processor 204 in the sleep state and user interface 202 inan inactive state. In some embodiments, state 1702 can be entered basedon inactivity, loss of focus, and/or other criteria.

State 1704 can be a “preheat” state that can be entered in response to apreheat event reported by preheat detection module 220 (e.g., at block1518 of FIG. 15). Upon entering preheat state 1704, wake control logic230 can signal applications processor 204 to start waking from its sleepstate. In some embodiments, waking of applications processor 204 has nouser-discernible effects (other than perhaps an increase in powerconsumption); the user need not be alerted to whether applicationsprocessor 204 is awake or asleep.

State 1706 can be a “possible gesture” state that can be entered inresponse to notification of a possible raise gesture (e.g., at block 412of FIG. 4 or block 812 of FIG. 8). State 1706 can be entered frompreheat state 1704 or directly from null state 1702. Upon enteringpossible gesture state 1706, wake control logic 230 can wakeapplications processor 204 (if this was not already done in preheatstate 1704) and can also activate user interface 202.

State 1708 can be a “detected gesture” state that can be entered inresponse to notification of a detected raise gesture (e.g., at block 418of FIG. 4, block 818 of FIG. 8, or block 1124 of FIG. 11). State 1708can be entered from possible gesture state 1706 or directly from nullstate 1702 or from preheat state 1704. For instance, in the embodimentdescribed above, process 1100 for detecting a deliberate raise gestureonly notifies wake control logic 230 of a detected raise gesture, whichcan occur either from null state 1702 or preheat state 1704. In thiscase, the possible gesture state 1706 might be skipped. In otherembodiments, process 1100 can notify wake control logic 230 of apossible wake gesture (e.g., upon detecting a first or second peak), anda direct transition from null state 1702 or preheat state 1704 todetected gesture state 1708 might not occur. Upon entering detectedgesture state 1708, wake control logic 230 can wake applicationsprocessor 204 and/or activate user interface 202 if either or both hasnot previously occurred.

State 1710 can be a “confirmed gesture” state that can be entered inresponse to notification of a confirmed raise gesture (e.g., at block424 of FIG. 4). In some embodiments, wake control logic 230 need not doanything in response to a transition to confirmed raise gesture state1710. However, wake control logic 230 can, if desired, take variousactions, such as sending a notification of the confirmation toapplications processor 204, and various applications or other processesexecuting on applications processor 204 can, if desired, behavedifferently in response to a confirmed raise gesture as opposed to adetected (but not confirmed) raise gesture.

State 1712 can be a “loss of focus” state that can be entered inresponse to notification of a loss-of-focus event (e.g., at block 1312of FIG. 13). Upon entering loss-of-focus state 1712, wake control logic230 can inactivate user interface 202 and can notify applicationsprocessor 204 of the loss of focus. In some embodiments, applicationsprocessor 204 might not immediately enter its sleep state in response toa loss of focus. For instance, applications processor 204 might continueto execute a process that started while device 200 was in a focus state(e.g., any of states 1706, 1708, 1710) until that process completes,then enter the sleep state.

From loss-of-focus state 1712, wake control logic 230 can transitionback to null state 1702 if applications processor 204 subsequentlyreturns to sleep state. In some embodiments, another focus-related event(e.g., preheat, possible raise gesture, detected raise gesture) mightoccur before applications processor 204 returns to its sleep state, inwhich case wake control logic 230 can return to the appropriate one ofstates 1704, 1706, 1708 without first retuning to null state, asindicated by the dashed arrows.

It is to be understood that the states shown in FIG. 17 are illustrativeand that other embodiments can define more, fewer, or different states.

In some embodiments, wake control logic 230 can selectively enable ordisable various gesture-detection algorithms or modules, including anyor all of preheat detection module 220 (e.g., implementing process1500), low-dynamic main detection module 222 (e.g., implementing process400), high-dynamic main detection module 224 (e.g., implementing process800), jiggle detection module 226 (e.g., implementing process 1100), andloss-of-focus detection module 228 (e.g., implementing process 1300),depending on the current state of wake control logic 230.

FIG. 18 is a flow diagram of a process 1800 that can be implemented inwake control logic 230 according to an embodiment of the presentinvention. Process 1800 can start (block 1802) in the null state of FIG.17. For purposes of description, it is assumed that at this stage,applications processor 204 is in its sleep state and user interface 202is inactive.

At block 1804, wake control logic 230 can enable one or moregesture-detection algorithms or modules to detect a raise gesture. Forexample, wake control logic 230 can enable preheat detection module 220,jiggle detection module 226, and one or the other of low-dynamic maindetection module 222 or high-dynamic main detection module 224. In someembodiments, high-dynamic main detection module 224 is enabled only whenthe user is engaged in high-dynamic activity, which can be determined asdescribed above, and low-dynamic main detection module 222 is enabledwhen the user is not engaged in high-dynamic activity. If the user'sactivity changes, wake control logic 230 can change which algorithm isenabled.

At block 1806, process 1800 can wait until one of the gesture-detectionalgorithms or modules provides a notification of an event. For example,preheat detection module 220 can notify wake control logic 230 of apreheat event, or low-dynamic main detection module 222 or high-dynamicmain detection module 224 can notify wake control logic 230 of apossible raise gesture. If such a notification is received, then atblock 1808, process 1800 can wake applications processor 204 (assumingit is not already awake) and disable preheat detection module 220. Otherraise-gesture detection algorithms or modules can continue to run.Depending on implementation, applications processor 204 might or mightnot activate user interface 202. For instance, in some embodiments,applications processor 204 activates user interface 202 in response to apossible raise gesture event but not in response to a preheat event.

At block 1810, wake control logic 230 can determine whether anotification of a detected raise gesture has been received. Such anotification can be received, e.g., from jiggle detection module 226 oreither of low-dynamic motion detection module 222 or high-dynamic motiondetection module 224. In some embodiments, if a notification of adetected raise gesture is not received within a timeout period after apreheat or possible raise gesture event, wake control logic 230 caninfer that the preheat or possible raise gesture was a false positive.Accordingly, at block 1812, wake control logic 230 can notifyapplications processor 204 of the false positive, re-enable preheatdetection module 220, and return to block 1804. In some embodiments, ifa threshold number of false-positive preheat events occur within a shortperiod of time, preheat detection module 220 can enter a “back-off”state, in which it can stop sending preheat notifications (or wakecontrol logic 230 can ignore preheat notifications) until the frequencyof false positives drops below a threshold. This can help reduceunnecessary power consumption by the applications processor.

If, at block 1810, a notification of a detected raise gesture isreceived, then at block 1814, process 1800 can enable gesture classifier234 to confirm the detected raise gesture and can disable jiggledetection module 226. In some instances, a notification of a detectedraise gesture can precede a notification of preheat or possible raisegesture (e.g., where jiggle detection module 226 generates thenotification of the detected raise gesture). Although not specificallyshown in FIG. 18, it should be understood that if this occurs, process1800 can perform operations of block 1808 together with those of block1814.

At block 1816, process 1800 can determine whether the detected raisegesture was confirmed. In some instances, confirmation at block 1816 canbe assumed (e.g., if the detected-raise-gesture notification at block1810 was received from jiggle detection module 226), and use of gestureclassifier 234 or the like to confirm a raise gesture is not required.In other instances, confirmation can be required in at least somecircumstances (e.g., if the detected-raise-gesture notification at block1810 was received from low-dynamic main detection module 222). Ifconfirmation is not received (and not assumed), or if disconfirmation isreceived, then at block 1818, wake control logic 230 can notifyapplications processor 204 of the unconfirmed or disconfirmed raisegesture, re-enable preheat detection module 220 and jiggle detectionmodule 226, and disable gesture classifier 234. Process 1800 can returnto block 1804 to continue to wait for a confirmed raise gesture.

If, at block 1816, the gesture is confirmed, then at block 1820, process1800 can instruct applications processor 204 to activate user interface202 (if it is not already active), enable loss-of-focus detection module228, and disable low-dynamic main detection module 222 or high-dynamicmain detection module 224. If jiggle detection module 226 or preheatmodule 220 are still enabled, these modules can also be disabled atblock 1820.

Process 1800 can wait at block 1822 until a notification of aloss-of-focus gesture is received, e.g., from loss-of-focus detectionmodule 228. During this time, device 200 can be considered to be infocus. Applications processor 204 can remain in its wake state, and userinterface 204 can remain active.

Once focus is lost, at block 1824, process 1800 can notify applicationsprocessor 204, inactivate user interface 202, and disable loss-of-focusdetection module 228. Process 1800 can return to block 1804 to re-enablevarious raise-gesture detection modules (e.g., jiggle detection module226 and one or the other of low-dynamic main detection module 222 andhigh-dynamic main detection module 224). If applications processor 204returns to the sleep state, process 1800 can re-enable preheat detectionmodule 220.

It will be appreciated that process 1800 is illustrative and thatvariations and modifications are possible. Steps described as sequentialmay be executed in parallel, order of steps may be varied, and steps maybe modified, combined, added or omitted. Activation of user interface204 can be controlled by wake control logic 230 or by a process inapplications processor 204, as desired. Preheat detection module 220 canrun continuously while applications processor 204 is in its sleep stateand can be disabled whenever applications processor 204 is in its wakestate. In some embodiments, loss of focus does not cause applicationsprocessor 204 to immediately return to sleep state. For example, anyprocessing tasks that are in progress on applications processor 204 cancontinue to execute, and applications processor 204 can return to sleepstate when such tasks are completed (assuming no further raise gestureor preheat event has occurred). Applications processor 204 can notifywake control logic 230 each time it transitions between wake and sleepstates, and wake control logic 230 can also be notified of state changesin user interface 202 (e.g., between inactive and active states). Wakecontrol logic 230 can enable or disable gesture detection modules oralgorithms based on notifications from applications processor 204, inaddition to the notifications received from the gesture detectionmodules or algorithms.

In the example shown in FIG. 18, the user interface is not activateduntil a raise gesture has been detected and confirmed. In someembodiments, it may be desirable to activate the user interface at anearlier stage (e.g., when a possible raise gesture or detected raisegesture is reported); this can result in more false positives but fewerfalse negatives and may provide a more responsive and satisfying userexperience. In addition, activation of the user interface can occur instages. For instance, the interface might be partially enabled (e.g.,display on but dimmed, touch overlay disabled or enabled at reducedresolution) when a notification of a possible raise gesture is received,then fully enabled when a notification of a detected raise gesture isreceived.

While the invention has been described with respect to specificembodiments, one skilled in the art will recognize that numerousmodifications are possible. For instance, although various algorithms ormodules are described above as being executed in a coprocessor on thedevice, those skilled in the art will recognize that a main processor(e.g., applications processor) can also execute any or all of thegesture detection algorithms or modules described above. As one example,in the embodiments described above, the gesture classifier can beinvoked selectively, at times when the applications processor is in itswake state, and the gesture classifier can be executed on theapplications processor rather than the coprocessor. Other algorithms canalso be executed entirely or partially on the applications processor,provided that the applications processor is in a wake state. In otherembodiments, the applications processor can have multiple power states.For example, the sleep state can include a state in which one section ofthe processor can execute gesture detection algorithms such as thosedescribed above while other sections of the processor are inactive toconserve power. (For instance, in a multi-core applications processor,one core might be active while the others are inactive.)

Adaptive control can be provided for the parameters used to detectpossible or actual raise gestures, to confirm detected raise gestures,and/or to detect preheat events or loss-of-focus events. Adaptivecontrol can allow the parameters to be tuned for more lenient or morestrict detection criteria. More lenient criteria can provide fasterresponse and earlier triggering, while more strict criteria can providefewer false positives (and therefore additional power saving).Parameters that can be tuned include the required amount of accruedy-tilt, the focus pose range of the device, and criteria on the devicetrajectory during execution of the raise gesture. In some embodiments,the tunable parameters can be modified via a configuration data block,and new configuration data can be downloaded to the device from time totime. A user interface can also be provided to adjust the tunableparameters (e.g., on a sliding scale from lenient to strict).

As another example, a raise gesture algorithm described above mayrequire that the device remain in a focus pose for a minimum dwell timebefore detecting a gesture. In some embodiments, dwell time can betraded off against accuracy of the focus pose. For instance, if thedevice remains close to but not in the range defined for focus pose(e.g., satisfying three of four criteria) and accrues enough dwell timein its position, this can be detected as a raise gesture. For example, asignificant rotation followed by holding an ending pose may berecognized even if the y-tilt is positive rather than zero or negative,assuming the ending pose is held long enough. Where dwell time is usedin this manner to “offset” failure to fully meet all focus-posecriteria, more strict focus-pose criteria can be specified.

Processes described herein can be used to determine when to activate auser interface for a device. Once activated, the user interface can bepresented in any state desired. For instance, the user interface can bepresented in a default “home” state, in the last state it was in priorto becoming inactive, in a state presenting a most recent notificationor information about notifications received since the user interface waslast active, or in any other state.

In some embodiments, a user interface or component thereof can beactivated in stages. For instance, when a possible raise gesture isdetected (e.g., as described above), the user interface can betransitioned to partial activation. Such partial activation may includeactivating a display but only dimly lighting it (where “dimly lighting”can include any light level lower than the normal operating brightnessof the display, which may depend, e.g., on ambient light, userpreferences, or the like), or activating a display but not atouch-sensitive overlay, activating a display but not a voice inputcircuit, etc. When the possible raise gesture becomes a detected raisegesture, the user interface can be transitioned to full activation,e.g., display on at standard brightness, touch-sensitive overlay active,voice input circuit activated, etc. As another example, differentcomponents of a user interface can be activated at different stages ofraise gesture detection. For example, when a possible raise gesture isdetected (e.g., as described above), one or more user interfacecomponent (e.g., a microphone or a display) can be activated while otheruser interface components (e.g., a touch-sensitive overlay on thedisplay, a speaker, a voice recognition coprocessor, or the like) remaininactive. When the possible raise gesture becomes a detected raisegesture, one or more other user interface components (e.g.,touch-sensitive overlay) can be activated. Further, one or more otheruser interface components (e.g., voice recognition coprocessor) canremain inactive until the detected raise gesture becomes a confirmedraise gesture. Other activation sequences can also be implemented, withdifferent user interface components transitioning to the active state inresponse to different gesture state transitions.

In some embodiments, wake control logic 230 can provide information toapplications processor 204 indicating how long device 200 has been in afocus state (e.g., the time elapsed since the most recent detected orconfirmed raise gesture event). Additionally or instead, applicationsprocessor 204 can infer the duration of a focus state based on timeelapsed since wake control logic 230 indicated a transition to focusstate (e.g., by notifying applications processor 204 of a detected orconfirmed raise gesture) and/or other information available toapplications processor 204. The duration of the focus state can be usedto affect the user experience. For example, suppose that device 200comes into focus displaying a notification (e.g., “New text message fromFred”). Depending on how long the user looks at the notification,applications processor 204 can choose to display additional informationabout the notification (e.g., content of the text message) without theuser having to operate a control. As another example, applicationsprocessor 204 can infer that the notification has been read if the userlooks for longer than a prescribed period of time and can automaticallyhide or dismiss the notification without the user having to operate acontrol. Other actions based on how long the user continues to hold thefocus pose can be implemented, such as scrolling or paging through alist of notifications or other items, or through content of a message.

Detecting a loss-of-focus gesture can have various consequences. Forexample, a user interface can be inactivated as described above.Additionally, any notification that was being displayed at the time ofloss of focus can be dismissed, or the read/unread state of anotification can be maintained.

Further, as described above, applications processor 204 can be notifiedby wake control logic 230 of gesture-state transitions or gesture events(e.g., possible raise gesture, detected raise gesture, confirmed raisegesture, loss of focus). In some embodiments, applications processor 204can also notify its clients (e.g., any applications and/or operatingsystem processes that may be executing on the applications processor) ofthese transitions, and the clients can take responsive action asdesired.

It should be understood that some embodiments of the invention can usefewer than all of the gesture detection modules described herein. Forinstance, some embodiments might include only a preheat detectionmodule. Some embodiments might include only a single natural raisegesture detection module (which can be, e.g., either a low-dynamic orhigh-dynamic detection module as described above), or multiple naturalraise gesture detection modules with no other modules. Some embodimentsmight include only a deliberate raise gesture detection module (e.g., ajiggle detection module as described above). Some embodiments mightinclude only a loss-of-focus detection module. Some embodiments mightinclude preheat and one or more natural raise gesture detection modules.Some embodiments might include preheat and deliberate raise gesturedetection modules. Some embodiments might include preheat andloss-of-focus detection modules. Some embodiments might include apreheat detection module, one or more natural raise gesture detectionmodules, and a deliberate raise gesture detection module. Someembodiments might include one or more natural raise gesture detectionmodules and a deliberate raise gesture detection module. Someembodiments might include one or more natural raise gesture detectionmodules, a deliberate raise gesture detection module, and aloss-of-focus detection module. Some embodiments might include adeliberate raise gesture detection module and a loss-of-focus detectionmodule. In addition, some embodiments might include additional gesturedetection modules not specifically described above.

It should also be understood that a device that implements automateddetection of a raise gesture and/or loss of focus gesture as describedabove might also provide a user-operable manual control (e.g., aphysical button, touch sensor, or the like) that can be used to activateand/or inactivate the user interface. Where such a control is provided,wake control logic 230 can receive notifications of changes in the stateof the user interface resulting from user operation of the manualcontrol and can adjust its own state accordingly (e.g., enabling ordisabling various algorithms descried above). Thus, while the automatedprocesses described herein can facilitate user interaction, the device(and the user) need not rely on them exclusively.

Various algorithms and parameters (e.g., weights, thresholds, othercriteria) described herein can be tuned heuristically, e.g., usingmachine learning and/or other techniques as described above. It iscontemplated that a training phase of the machine learning can beperformed during device development (e.g., prior to widespreaddistribution), and the results of the training can be incorporated intodevice firmware. Thus, it is not necessary for users to perform devicetraining. In some embodiments, the device may be able to collectfeedback during ordinary operation, e.g., recording relevant intervalsof motion-sensor data in instances where the user executes thedeliberate raise gesture or operates a manual control, which mayindicate that a natural raise gesture detection algorithm produced afalse negative. The device may be able to execute training algorithms inthe background to refine its own algorithms and parameters based on suchrecorded data. In some embodiments, a device manufacturer can aggregatesuch data across a large set of devices and use the information toupdate the gesture-detection algorithms and/or parameters. (To protectuser privacy, the aggregation can be done anonymously and can be limitedto the motion-sensor data and an indication that the data may correspondto a false negative.)

The present disclosure uses terms such as “approximately” and“substantially” to qualify certain measurements, such as stability infocus pose. Those skilled in the art will appreciate that most userscannot hold their arms perfectly still and that these terms are used toindicate that allowances may be made for the effects of natural userinstability as well as the inherent accuracy of the various motionsensors. Other terms such as horizontal, vertical, and parallel may besimilarly qualified, to indicate that physical perfection isunnecessary. Further, terms such as “in the line of sight” as usedherein generally refer to assumptions about the orientation of theuser's head relative to the device, and such assumptions might notalways match the ground truth of whether the user's eyes are or are notdirected toward the device.

Further, while the description makes specific references to wearabledevices and wrist-wearable devices, embodiments of the invention are notlimited to wearable or wrist-wearable devices. For instance, thealgorithms and modules described above can be implemented in otherportable devices, such as mobile phones, tablets, or the like, that auser might pick up and hold during interaction with the device.Algorithms and/or modules as described above, when implemented in ahandheld device, can detect changes in the orientation of the deviceconsistent with being picked up and held in a user's line of sight (orconversely changes consistent with being put down or put away), anddetection of such changes can be used to trigger changes in device state(e.g., activating a display or other user interface component, waking aprocessor from a sleep state, etc.).

Embodiments of the present invention can be realized using anycombination of dedicated components and/or programmable processorsand/or other programmable devices. The various processes describedherein can be implemented on the same processor or different processorsin any combination. Where components are described as being configuredto perform certain operations, such configuration can be accomplished,e.g., by designing electronic circuits to perform the operation, byprogramming programmable electronic circuits (such as microprocessors)to perform the operation, or any combination thereof. Further, while theembodiments described above may make reference to specific hardware andsoftware components, those skilled in the art will appreciate thatdifferent combinations of hardware and/or software components may alsobe used and that particular operations described as being implemented inhardware might also be implemented in software or vice versa.

Computer programs incorporating various features of the presentinvention may be encoded and stored on various computer readable storagemedia; suitable media include magnetic disk or tape, optical storagemedia such as compact disk (CD) or DVD (digital versatile disk), flashmemory, and other non-transitory media. (It is understood that “storage”of data is distinct from propagation of data using transitory media suchas carrier waves.) Computer readable media encoded with the program codemay be packaged with a compatible electronic device, or the program codemay be provided separately from electronic devices (e.g., via Internetdownload or as a separately packaged computer readable storage medium).

Certain embodiments relate to methods for detecting a raise gesture in adevice, such as a wrist-wearable device or other wearable device, whichcan have a user interface component having an active state and aninactive state, a motion sensor to detect motion of the device, and atleast a first processor. For example, the first processor can determine,based on a set of motion sensor data samples corresponding to a timeinterval, a starting pose corresponding to a beginning of the timeinterval. The first processor can determine, based at least in part onthe starting pose, a set of criteria for identifying a possible raisegesture using the set of motion sensor data samples. The first processorcan further determine a possible raise gesture based at least in part onwhether the set of motion sensor data samples satisfies the selected setof criteria. The first processor can further determine a detected raisegesture in the event that the possible raise gesture is followed by atleast a minimum period of dwell time in a focus pose. The firstprocessor can notify another component of the device when a possibleraise gesture is identified and when a detected raise gesture isidentified.

In some embodiments, the other component can include a user interfacecomponent. The user interface component can be activated in response tobeing notified of the possible raise gesture or in response to beingnotified of the detected raise gesture. In some embodiments, the userinterface component can transition from an inactive state to a partiallyactive state in response to being notified of the possible raise gestureand from the partially active state to an active state in response tobeing notified of the detected raise gesture.

In some embodiments, the other component can include an applicationsprocessor. The applications processor can, for example, transition froma sleep state to a wake state in response to being notified of thepossible raise gesture and can activate a user interface component ofthe device in response to being notified of the possible raise gestureor in response to being notified of the detected raise gesture.

A starting pose can be determined in various ways. In some embodiments,determining the starting pose can include comparing one or more oldestmotion sensor data samples in the set of motion sensor data samples toeach of a plurality of canonical starting poses and selecting one (ormore) of the canonical starting poses based on the comparison. In someembodiments, if more than one canonical starting pose is selected, thestarting pose can be defined as a blend of the selected canonicalstarting poses. In some embodiments, determining the starting pose caninclude identifying a current user activity using an activity classifierand determining the starting pose based at least in part on the currentuser activity.

The set of criteria for identifying a possible raise gesture can bedetermined in various ways. For example, determining the set of criteriafor identifying a possible raise gesture can include accessing a lookuptable using the determined starting pose and extracting the set ofcriteria from the lookup table. Where the starting pose is defined as ablend of two or more selected canonical staring poses, determining theset of criteria for identifying a possible raise gesture can includeaccessing a lookup table using each of the selected canonical startingposes, extracting a set of criteria corresponding to each of theselected canonical starting poses from the lookup table, and blendingthe extracted sets of criteria.

In some embodiments, the set of criteria for identifying a possibleraise gesture can depend on the available motion sensor data. Forinstance, if the motion sensor data includes accelerometer data, theselected set of criteria for identifying a possible raise gesture caninclude any or all of: a criterion based on an accrued tilt determinedfrom the accelerometer data during the time interval; a criterion basedon an amount of lifting of the device, the amount of lifting determinedfrom the accelerometer data during the time interval; and/or a criterionbased on smoothness of the motion during the time interval. As anotherexample, if the motion sensor data includes gyroscope data from agyroscopic sensor, the selected set of criteria for identifying apossible raise gesture can include a criterion based on an accruedrotation about an axis substantially parallel to a user's forearm, theaccrued rotation being determined from the gyroscope data during thetime interval. In some embodiments where the motion sensor data includesboth gyroscope data from a gyroscopic sensor and accelerometer data froman accelerometer, the gyroscope data can be used to identify thepossible raise gesture while the accelerometer data is used to identifythe detected raise gesture.

The possible raise gesture can be determined in various ways. Forexample, determining the possible raise gesture can include determining,based on the set of motion sensor data samples, an ending posecorresponding to an end of the time interval and determining whether theending pose corresponds to the focus pose. In some embodiments,determining the possible raise can include determining whether a motionfrom the starting pose to an ending pose corresponding to an end of thetime interval slows or stops by the end of the time interval.

The focus pose can be defined in various ways. In some embodiments, thefocus pose is defined based at least in part on the starting pose. Insome embodiments, the focus pose can be defined as corresponding to arange of orientations of the device, and the minimum period of dwelltime in the focus pose can be determined based at least in part on alocation of a current orientation of the device relative to the range oforientations corresponding to the focus pose. In some embodiments wherethe focus pose is defined as corresponding to a range of orientations ofthe device, an ending pose of the possible raise gesture can beidentified and a dwell time in the ending pose determined; the range oforientations corresponding to the focus pose can be dynamically adjustedbased at least in part on the dwell time in the ending pose, forexample, such that the range increases with an increase in the dwelltime.

In some embodiments, the criteria for determining a possible raisegesture can be selectable within a range from lenient to strict.Likewise, a definition of the focus pose (e.g., a range of orientationsof the device corresponding to the focus pose) can be adjustable withina range from lenient to strict. The user may be able to select or adjustthe leniency or strictness.

In some embodiments, subsequently to determining the detected raisegesture, a gesture classifier can be used to confirm the detected raisegesture. For example, a confidence score can be assigned to the detectedraise gesture, and features of interest can be input into the gestureclassifier. In embodiments where the motion sensor data includesaccelerometer data, features of interest can include, for example, anyor all of: accelerometer data samples corresponding to a time window ofinterest; a smoothness parameter based on a standard deviation ofchanges between consecutive accelerometer data samples; an accrued tiltrelative to an axis parallel to a user's forearm (e.g., for awrist-wearable device); a starting orientation of the device at abeginning of a time window of interest (e.g., a time during which thedetected raise gesture occurred); and/or an ending orientation of thedevice at an ending of a time window of interest. In embodiments wherethe motion sensor data includes gyroscope data samples from a gyroscopicsensor, features of interest can include, for example, any or all of:individual gyroscope data samples corresponding to a time window ofinterest; a smoothness parameter based on a standard deviation ofchanges between consecutive gyroscope data samples; an accrued rotationrelative to an axis parallel to a user's forearm; a starting orientationof the device at a beginning of the time window of interest; and/or anending orientation of the device at an ending of the time window ofinterest.

The gesture classifier, which can include, e.g., a Bayesian classifierimplementing a linear discriminant analysis, can compute, from thefeatures of interest, a probability that the detected raise gesture is atrue raise gesture, the probability computed from the features ofinterest. Based on the confidence score and the probability, adetermination can be made as to whether to confirm the raise gesture.For example, a threshold value for the probability can be selected, withthe selection based at least in part on the confidence score, and thedetermination can be made based on whether the probability exceeds thethreshold value. In some embodiments, determining whether to confirm thedetected raise gesture can include determining whether to wait foradditional motion sensor data prior to either confirming ordisconfirming the raise gesture. In some embodiments, the gestureclassifier can be previously trained to distinguish a natural raisegesture from at least one other similar gesture.

In some embodiments, a user interface component of the device can beactivated in response to confirmation by the gesture classifier, or auser interface component of the device can be inactivated in the eventthat the gesture classifier disconfirms an identified detected raisegesture.

In addition to detecting a raise gesture, in some embodiments, thedevice can also detect preheat events. For example, the first processor(or another processor) can execute a preheat detection algorithm todetect initiation of the raise gesture, where the preheat detectionalgorithm executes concurrently with performing the determining,selecting, and identifying acts associated with detecting a naturalraise gesture. The processor can notify the other component (e.g., anapplications processor) of a preheat event in the event that initiationof the raise gesture is detected. A preheat algorithm can include, forexample, analyzing a set of one or more recent motion sensor datasamples to detect a possible initiation of a raise gesture; and in theevent that a possible initiation of a raise gesture is not detected,repeating the analyzing for a subsequent motion sensor data sample; andin the event that a possible initiation of a raise gesture is detected,evaluating each of a sequence of subsequent motion sensor data samplesas either consistent or inconsistent with a raise gesture; the othercomponent can be notified of the preheat event in the event that a firstthreshold number of motion sensor data samples consistent with a raisegesture is reached before a second threshold number of motion sensordata samples inconsistent with a raise gesture is reached. The othercomponent (e.g., an applications processor) can transition from a sleepstate to a wake state in response to the preheat event. In someembodiments, in the event that the notification of the preheat event isnot followed by a notification of a detected raise gesture within atimeout period, the other component can transition from the wake stateback to the sleep state. In some embodiments, initiation of the raisegesture can be detected at a time sufficiently early to allow theapplications processor to complete the transition to the wake state bythe time the detected raise gesture is identified. In some embodiments,the notification of the preheat event does not affect an inactive userinterface component of the device.

Such methods can be implemented in various devices. For example, thedevice can have user interface components such as any or all of adisplay (which can be a touch screen display or other display), amicrophone, a speaker, and/or a button. The device can have variousmotion sensors, such as an accelerometer and/or a gyroscopic sensor.Detection of a raise gesture as described herein can be performed in aprimary applications processor or in a coprocessor as desired.

Some devices can include a user interface component having an activestate and an inactive state, a motion sensor operable to generate motionsensor data indicative of motion of the device, and a motion processingunit coupled to the user interface component and the motion sensor. Themotion processing unit can include a natural detection module thatincorporates: a starting pose estimation unit to receive motion sensordata and to estimate a starting pose based on the motion sensor data; apossible raise gesture determining unit to receive motion sensor data,to determine whether the received data satisfy criteria for a possibleraise gesture, and to generate a notification of a possible raisegesture in the event that the criteria are satisfied; and a detectedraise gesture determining unit to receive the notification of thepossible raise gesture from the possible raise gesture determining unit,to monitor additional accelerometer data to determine whether acondition is met for a detected raise gesture, and to generate anotification of a detected raise gesture in the event that the conditionis met. In some embodiments, the motion processing unit can also includea criteria determining unit to determine criteria for detecting apossible raise gesture based at least in part on the starting poseestimated by the starting pose estimation unit and to provide thecriteria to the possible raise gesture determining unit. In someembodiments, the motion processing unit can also include a confirmationunit to perform gesture confirmation based on motion sensor dataassociated with a detected raise gesture and to generate a notificationof a confirmed or disconfirmed raise gesture. In some embodiments, thenatural detection module can be configured to identify a gesture statefrom a set of gesture states that includes a null state, a possibleraise gesture state, and a detected raise gesture state. For example, insome embodiments, the possible raise gesture state can be identifiedbased at least in part on a starting pose determined from the motionsensor data and a set of criteria for a change from the starting pose toan ending pose, the set of criteria being selected based at least inpart on the starting pose. In some embodiments, the detected raisegesture state can be identified based at least in part on a dwell timein a focus pose.

Certain embodiments relate to methods for detecting a deliberate raisegesture in a device, such as a wrist-wearable device, which can have auser interface component having an active state and an inactive state, amotion sensor (e.g., an accelerometer and/or a gyroscopic sensor) todetect motion of the device, and at least a first processor. Forexample, the first processor can collect a set of motion sensor datasamples from a motion sensor of the device, the set of motion sensordata samples corresponding to a time interval. The first processor candetect a first impulse peak and a second impulse peak in the motionsensor data samples, the first and second impulse peaks each indicatingmovement in a direction corresponding to a rotation of a wrist of a userwearing the device (e.g., on the assumption that the device is beingworn on the user's wrist), the first and second impulse peaks beingseparated in time by a period less than a timeout period. The firstprocessor can detect a raise gesture (e.g., a deliberate raise gesture)based at least in part on detecting the first and second impulse peaksand can notify another component of the device in the event that a raisegesture is detected. In some embodiments, the first processor canfurther determine that, following the second impulse peak, the device isheld in an approximately stable position for at least a minimum dwelltime, with the raise gesture being detected based in part on detectingthe first and second impulse peaks and in part on determining that thedevice is held in the approximately stable position. In someembodiments, the first processor can also determine, based on the motionsensor data samples, whether the device is in a primed position at abeginning of the time interval. The primed position can be determined,e.g., based at least in part on determining whether the device is heldstill for a minimum period of time and/or on determining an orientationof the device and comparing the orientation to an assumed orientationassumed to position the device in a line of sight of a user operatingthe device. In some embodiments, determining whether the device is in aprimed position can be based at least in part on information about acurrent activity of a user operating the device.

Impulse peaks can be detected in various ways. For instance, inembodiments where the motion sensor includes an accelerometer, detectingthe first and second impulse peaks can be based at least in part on ajerk determined from accelerometer data samples.

Detection of a raise gesture based on impulse peaks can be used, e.g.,to transition an applications processor from a sleep state to a wakestate in response to being notified of the raise gesture and/or totransition a user interface component from an inactive state to anactive state in response to being notified of the raise gesture.

Such methods can be implemented in various devices. For example, thedevice can have user interface components such as any or all of adisplay (which can be a touch screen display or other display), amicrophone, a speaker, and/or a button. The device can have variousmotion sensors, such as an accelerometer and/or a gyroscopic sensor.Detection of a deliberate raise gesture as described herein can beperformed in a primary applications processor or in a coprocessor asdesired.

Some devices can include a user interface component having an activestate and an inactive state, a motion sensor operable to generate motionsensor data indicative of motion of the device, and a motion processingunit coupled to the user interface component and the motion sensor. Themotion processing unit can include a deliberate detection module thatincorporates: a priming detection unit to receive motion sensor data andto determine from the motion sensor data whether the user's arm isprimed to execute a deliberate raise gesture; an impulse peak detectionunit to receive additional motion sensor data and detect the presence ofa target number of impulse peaks based on the additional motion sensordata; and a stability detection unit to receive further motion sensordata and determine whether the further motion sensor data indicates thatthe device position has stabilized following detection of the targetnumber of impulse peaks by the impulse peak detection unit.

Certain embodiments relate to methods for detecting a preheat eventcorresponding to an initiation of a raise gesture in a device, such as awrist-wearable device or other wearable device, which can have a userinterface component having an active state and an inactive state, amotion sensor to detect motion of the device, and at least a firstprocessor. For example, a motion sensor (e.g., an accelerometer) of thedevice can be operated to collect data samples at a sampling rate. Afirst processor in the device can detect a possible initiation of araise gesture based at least in part on a most recent data sample. Inthe event that a possible initiation of a raise gesture is not detected,the first processor can repeat the analyzing for a subsequent datasample. In the event that a possible initiation of a raise gesture isdetected, the first processor can evaluate each of a sequence ofsubsequent data samples as either consistent or inconsistent with araise gesture. The first processor can notify another component of thedevice of a preheat event in the event that a first threshold number ofsubsequent data samples consistent with a raise gesture is reachedbefore a second threshold number of subsequent data samples inconsistentwith a raise gesture is reached. In some embodiments, in the event thatthe second threshold number of subsequent data samples inconsistent witha raise gesture is reached before the first threshold number ofsubsequent data samples consistent with the raise gesture is reached,the detection process can return to an initial state in which a possibleinitiation of a raise gesture has not been detected and repeat thedetecting of a possible initiation of a raise gesture.

In some embodiments, the other component can include an applicationsprocessor. The applications processor can, for example, transition froma sleep state to a wake state in response to the notification of thepreheat event. This can occur without affecting a state of a userinterface component of the device. In some embodiments, the applicationsprocessor can transition from the wake state to the sleep state in theevent that the notification of the preheat event is not followed by anotification of a raise gesture within a timeout period.

Possible initiation of a raise gesture can be detected in various ways.For example, two most recent data samples can be compared to detect achange in position or orientation of the device, and it can bedetermined whether the detected change is in a direction consistent withinitiation of a raise gesture. In some embodiments, detecting a possibleinitiation of a raise gesture can be based at least in part on astarting pose determined from the data samples.

In some embodiments where the device is a wrist wearable device with anaccelerometer, detecting a possible initiation of a raise gesture caninclude: determining a change in a first component of an accelerationvector, the first component being in a direction approximately parallelto a forearm of a user wearing the device; determining a change in asecond component of the acceleration vector, the second component beingin a direction orthogonal to the first direction and in a plane of adisplay of the device; and detecting the possible initiation of theraise gesture based on a combination of the changes in the firstcomponent and the second component.

Evaluating subsequent data samples can be performed in various ways. Forexample, the evaluation can be based at least in part on any or all of:evaluation of whether a change in one or both of a position or anorientation of the device, as determined from the data samples, isconsistent with continuing a raise gesture; a measurement of asmoothness of the motion based on the data samples; a starting pose at atime when the possible initiation of the raise gesture was detected;and/or a trajectory of the device inferred from the data samples.

In some embodiments, subsequently to notifying the other component ofthe preheat event, the first processor can continue to evaluate each ofa sequence of subsequent data samples as either consistent orinconsistent with a raise gesture and can notify the other component ofa loss of preheat event in the event that the subsequent data samplesbecome inconsistent with a raise gesture.

Such methods can be implemented in various devices. For example, thedevice can have user interface components such as any or all of adisplay (which can be a touch screen display or other display), amicrophone, a speaker, and/or a button. The device can have variousmotion sensors, such as an accelerometer and/or a gyroscopic sensor.Detection of a preheat event as described herein can be performed in aprimary applications processor or in a coprocessor as desired.

Some devices can include a user interface component having an activestate and an inactive state, a motion sensor operable to generate motionsensor data indicative of motion of the device, and a motion processingunit coupled to the user interface component and the motion sensor. Themotion processing unit can include a preheat detection module thatincorporates: a possible gesture start determination unit to receivemotion sensor data samples and to determine, based on the motion sensordata, whether a possible gesture start has occurred; a sample evaluationunit to receive motion sensor data samples and to evaluate each motionsensor data sample to determine whether it is consistent or inconsistentwith a continuation of a possible raise gesture; a counter unit tomaintain a first counter to count samples that are determined by thesample evaluation unit to be consistent with a continuation of apossible raise gesture and a second counter to count samples that aredetermined by the sample evaluation unit to be inconsistent with acontinuation of a possible raise gesture; and a preheat determinationunit to receive the first and second counter values from the counterunit and to determine whether a preheat event has occurred.

Certain embodiments relate to methods for detecting a loss-of-focusevent in a device, such as a wrist-wearable device or other wearabledevice, which can have a user interface component having an active stateand an inactive state, a motion sensor (e.g., an accelerometer and/or agyroscopic sensor) to detect motion of the device, and at least a firstprocessor. For example, the first processor can establish the device isin a focus state, where the focus state includes a user interfacecomponent of the device being in an active state. The first processorcan receive a sequence of motion sensor data samples (e.g.,accelerometer data samples and/or gyroscope data samples) from a motionsensor of the device. The first processor can detect a change in anorientation (e.g., change in a tilt angle) of the device based on themotion sensor data samples. The first processor can identify aloss-of-focus gesture based at least in part on the change in theorientation. The first processor can notify another component of thedevice when the loss-of-focus gesture is detected.

In some embodiments where the motion sensor data samples includeaccelerometer data samples from an accelerometer and gyroscope datasamples from a gyroscopic sensor, the first processor can select whetherto use accelerometer data samples or gyroscope data samples, theselection being based at least in part on a current activity of theuser.

Change in orientation can be detected in various ways. For example,detecting the change in the orientation can include determining areference tilt angle while the device is in the focus state anddetermining a net change in the tilt angle relative to the referencetilt angle, where the change in the orientation includes the net changein the tilt angle. The reference tilt angle can be determined, e.g.,based at least in part on an orientation of the device determined basedon motion sensor data samples representing a beginning of a time window.In addition or instead, the reference tilt angle is determined based atleast in part on an accrued tilt associated with a previously detectedraise gesture. In the latter case, the loss-of-focus gesture can beidentified in the event that the change in the tilt angle corresponds toa loss of more than a threshold amount of the accrued tilt.

Other techniques for identifying loss of focus can be implemented. Forexample, the loss-of-focus gesture can be identified in the event thatthe change in the orientation exceeds a threshold and/or in the eventthat the change in the orientation continuously exceeds a threshold forat least a minimum amount of time. In some embodiments, a duration ofthe focus state can be determined, and the minimum amount of time can bebased at least in part on the duration of the focus state; for instance,the minimum amount of time can increase as the duration of the focusstate increases. In some embodiments, identifying the loss-of-focusgesture can be based in part on the change in the orientation and inpart on a current activity of a user, which can be determined, e.g.,using an activity classifier.

Such methods can be implemented in various devices. For example, thedevice can have user interface components such as any or all of adisplay (which can be a touch screen display or other display), amicrophone, a speaker, and/or a button. The device can have variousmotion sensors, such as an accelerometer and/or a gyroscopic sensor.Detection of a loss-of-focus gesture as described herein can beperformed in a primary applications processor or in a coprocessor asdesired.

Some devices can include a user interface component having an activestate and an inactive state, a motion sensor operable to generate motionsensor data indicative of motion of the device, and a motion processingunit coupled to the user interface component and the motion sensor. Themotion processing unit can include a loss-of-focus detection module thatincorporates: an orientation determining unit to receive motion sensordata and to determine an orientation for the device based on the motionsensor data; an orientation change detection unit to determine, based atleast in part on the orientation determined by the orientationdetermining unit, whether a change in orientation has occurred; an armposition estimation unit to receive motion sensor data and to determinefrom the data an estimated arm position of an arm on which the device ispresumed to be worn; and a focus determination unit to receiveorientation change information from the orientation change detectionunit, to receive the estimated arm position from the arm positionestimation unit, and to determine, based at least in part on thereceived orientation change information and estimated arm position,whether loss of focus has occurred.

Certain embodiments relate to methods for detecting various raisegestures (including any combination of natural raise gestures,deliberate raise gestures, preheat events, and/or loss-of-focusgestures, e.g., as described above) in a device, such as awrist-wearable device or other wearable device, which can have a userinterface component having an active state and an inactive state, amotion sensor to detect motion of the device, and one or moreprocessors. Motion sensor data can be received from a motion sensor ofthe device. The motion sensor data can be processed using a set ofgesture detection modules (including, e.g., any one or more of thenatural raise gesture detection modules, deliberate raise gesturedetection modules, and/or preheat detection modules described above) todetect one or both of a raise gesture indicative of a user moving thedevice into a presumed line of sight or a preheat event indicative ofinitiation of the raise gesture. An applications processor of the devicecan be notified in the event that a preheat event is detected, and theapplications processor can transition from a sleep state to a wake statein response to the notification of the preheat event. A user interfacecomponent of the device can be notified in the event that the raisegesture is detected, and the user interface component can transitionfrom an inactive state to an active state in response to thenotification of the raise gesture. In some embodiments, the applicationsprocessor transitions from the sleep state to the wake state in responseto the notification of the raise gesture in the event that the raisegesture is detected prior to detecting the preheat event. In someembodiments, subsequently to detecting the raise gesture, the set ofdetection modules can be disabled and a loss-of-focus detection module(e.g., as described above) can be enabled.

Certain embodiments relate to methods that can be executed in a device,such as a wrist-wearable device or other wearable device, which can havea user interface component having an active state and an inactive state,a motion sensor to detect motion of the device, and one or moreprocessors. A null state can be established in which an applicationsprocessor of the device is in a sleep state and a user interfacecomponent of the device is in an inactive state. A coprocessor of thedevice can execute a set of gesture detection algorithms including oneor more raise gesture detection algorithms to detect a raise gesture(e.g., natural or deliberate raise gestures as described above) and apreheat detection algorithm to detect an initiation of the raise gesture(e.g., as described above). The preheat detection algorithm can generatea preheat event in the event that the initiation of the raise gesture isdetected. At least one of the raise gesture detection algorithms cangenerate a raise gesture event in the event that the raise gesture isdetected. The applications processor can be transitioned from the sleepstate to a wake state in response to the preheat event. The userinterface component can be transitioned from the inactive state to anactive state in response to the raise gesture event. In someembodiments, in the event that the raise gesture detection algorithmgenerates the raise gesture event before the preheat detection algorithmgenerates the preheat event, the applications processor can betransitioned from the sleep state to a wake state in response to theraise gesture event. In some embodiments, the preheat detectionalgorithm can be disabled when the applications processor is in the wakestate and can be reenabled in the event that the applications processortransitions from the wake state to the sleep state. In some embodiments,all of the raise gesture detection algorithms can be disabled when theuser interface component is in the active state, and at least one of theraise gesture detection algorithm can be reenabled in the event that theuser interface component transitions from the active state to theinactive state.

In some embodiments, the raise gesture detection algorithms can includeone or more natural raise gesture detection algorithms, such as a firstnatural raise gesture detection algorithm to detect a raise gesture in alow-dynamic environment and/or a second natural raise gesture detectionalgorithm to detect a raise gesture in a high-dynamic environment. Insome embodiment where both the first and second natural raise gesturedetection algorithms are included, one of the first or second naturalraise gesture detection algorithms can be selected to be executed at agiven time, the selection being based at least in part on a current useractivity, which can be determined, e.g., using an activity classifierand/or a data quality analysis of accelerometer data. In someembodiments, a deliberate raise gesture detection algorithm can be usedin combination with either or both of the first and second natural raisegesture detection algorithms.

In some embodiments, a first one of the one or more raise gesturedetection algorithms can generate multiple different raise gestureevents including a possible raise gesture event and a detected raisegesture event. Where this is the case, transitioning the user interfacecomponent to the active state can occur in response to the detectedraise gesture event. In some embodiments, the user interface componentcan be transitioned to a partially active state in response to thepossible raise gesture event and transitioned to a fully active state inresponse to the detected raise gesture event. In some embodiments, theapplications processor can transition from the sleep state to the wakestate in the event that a possible raise gesture event is detectedbefore a preheat event is detected.

In some embodiments, a first one of the one or more raise gesturedetection algorithms can generate multiple different raise gestureevents including a possible raise gesture event, a detected raisegesture event, and a confirmed raise gesture event. Where this is thecase, transitioning the user interface component to the active state canoccur in response to the confirmed raise gesture event.

In some embodiments, in response to the raise gesture event, aloss-of-focus detection algorithm can be executed to detect aloss-of-focus event (e.g., as described above). In response to detectingthe loss-of-focus event, the user interface component can betransitioned from the active state to the inactive state.

In some embodiments, after detecting the raise gesture event, a dwelltime of the device in a focus pose can be determined and a presentationof information at the user interface component can be modified based atleast in part on the dwell time. For example, a presented informationitem can be changed from a first information item to a secondinformation item; additional information about an initially presentedinformation item can be presented; or an initially presented informationitem can cease to be presented.

Such methods can be implemented in various devices, includingwrist-wearable devices and other wearable devices. For example, thedevice can have a user interface component having an active state and aninactive state; an applications processor coupled to the user interfacecomponent, the applications processor having a sleep state and a wakestate; a coprocessor coupled to the applications processor; and a motionsensor (e.g., accelerometer and/or gyroscopic sensor) to detect motionof the device, the being motion sensor coupled to the coprocessor. Thecoprocessor can be configured to process motion sensor data receivedfrom the motion sensor using various processing algorithms (some or allof which can be concurrently operable) to detect gesture related eventsincluding preheat events and raise gestures (including any or all of thealgorithms described above) and to notify the applications processor ofthe preheat events and raise gestures. The applications processor can beconfigured to transition from the sleep state to the wake state inresponse to a notification of a preheat event and to instruct the userinterface component to transition from the inactive state to the activestate in response to a notification of a raise gesture. In someembodiments, the applications processor can be further configured totransition from the sleep state to the wake state in the event that anotification of a raise gesture is received while the applicationsprocessor is in the sleep state.

Various combinations of processing algorithms can be used, depending inpart on available motion sensors. For instance, in some embodimentswhere the motion sensor includes an accelerometer and a gyroscopicsensor, the processing algorithms can include a low-dynamic detectionalgorithm to detect a natural raise gesture based on data from theaccelerometer and a high-dynamic detection algorithm to detect a naturalraise gesture based at least in part on data from the gyroscopic sensor.In some embodiments, the coprocessor can be configured to determine acurrent activity of the user as either a low-dynamic activity or ahigh-dynamic activity and to disable one of the low-dynamic detectionalgorithm or the high-dynamic detection algorithm based on the currentactivity of the user. Determining the current activity of the user canbe based at least in part on an activity classifier and/or a dataquality analysis performed on accelerometer data samples.

In some embodiments, the processing algorithms can include aloss-of-focus algorithm to detect a loss-of-focus event corresponding toa user moving a device out of a focus pose, and the coprocessor can befurther configured to notify the applications processor when theloss-of-focus event is detected. In some embodiments, the applicationsprocessor can be further configured to transition the user interface tothe inactive state in response to the notification of the loss-of-focusevent. In some embodiments, the coprocessor can be configured to enablethe loss-of-focus algorithm and disable all of the gesture detectionalgorithms in response to detecting the raise gesture and to enable atleast two of the gesture detection algorithms and disable theloss-of-focus algorithm in response to detecting the loss-of-focusevent.

The user interface component can include, for example, a display thatcan be powered off when the user interface component is in the inactivestate and powered on when the user interface component is in the activestate. As another example, the user interface component can include atouch screen display that can be powered off when the user interfacecomponent is in the inactive state and powered on when the userinterface component is in the active state.

In some embodiments, at least one of the processing algorithms can becapable of detecting a possible raise gesture, and the coprocessor canbe further configured to notify the applications processor of a possibleraise gesture. The applications processor can be configured to instructthe user interface component to transition from the inactive state to apartially active state in response to a notification of a raise gesture.For example, the user interface component can include a display that canbe powered off when the user interface component is in the inactivestate, powered on in a dimmed state when the user interface component isin the partially active state, and powered on in a normal brightnessstate when the user interface component is in the active state.

In some embodiments, the device can include a user input controloperable to manually activate the user interface component. Thecoprocessor can be configured to receive a notification in the eventthat the user input control is operated to manually activate the userinterface component. (As described above, this can be used for tuning,training, or other experience-based modifications to the gesturedetection algorithms.)

Any combination of processing algorithms can be used, including any orall of: an algorithm to detect a natural raise gesture; an algorithm todetect a natural raise gesture in a low-dynamic environment; analgorithm to detect a natural raise gesture in a high-dynamicenvironment; an algorithm to detect a preheat event; an algorithm todetect a deliberate raise gesture (e.g., a jiggle gesture as describedabove); and/or an algorithm to detect a loss-of-focus gesture.

Certain embodiments of the present invention relate to devices that caninclude a user interface component having an active state and aninactive state, a motion sensor (e.g., an accelerometer and/or agyroscopic sensor) operable to generate motion sensor data indicative ofmotion of the device, one or more gesture detection modules, each of thegesture detection modules being operable to determine a gesture state ofthe device based at least in part on the motion sensor data, and wakecontrol logic coupled to the one or more gesture detection modules. Thewake control logic can be configured to receive gesture stateinformation from the one or more gesture detection modules and to sendnotifications to the user interface component based on the receivedgesture state information. In some embodiments, the wake control logiccan also be configured to selectively enable or disable different onesof the gesture detection modules based at least in part on the receivedgesture state information.

In some embodiments, the device can also include an applicationsprocessor coupled to the user interface component, the applicationsprocessor having a sleep state and a wake state. The wake control logiccan be configured to send notifications to the applications processorbased on the received gesture state information. In some embodiments,the wake control logic can be configured to send the notifications tothe user interface component via the applications processor. In someembodiments, the applications processor can be configured to transitionfrom a sleep state to a wake state in response to a first notificationfrom the wake control logic, the first notification indicating detectionof a preheat event by one of the gesture detection modules. Theapplications processor can be further configured to transition from asleep state to a wake state in response to a second notification fromthe wake control logic, the second notification indicating detection ofa raise gesture by one of the gesture detection modules.

In some embodiments, the user interface component can be configured totransition from a sleep state to a wake state in response to a secondnotification from the wake control logic, the second notificationindicating detection of a raise gesture by one of the gesture detectionmodules.

The gesture detection modules can include any or all of the gesturedetection modules described above. For example, the gesture detectionmodules can include a preheat detection module operable to detect apreheat event corresponding to a beginning of a raise gesture. Thepreheat detection module can include: a possible gesture startdetermination unit to receive motion sensor data samples and todetermine, based on the motion sensor data, whether a possible gesturestart has occurred; a sample evaluation unit to receive motion sensordata samples and to evaluate each motion sensor data sample to determinewhether it is consistent or inconsistent with a continuation of apossible raise gesture; a counter unit to maintain a first counter tocount samples that are determined by the sample evaluation unit to beconsistent with a continuation of a possible raise gesture and a secondcounter to count samples that are determined by the sample evaluationunit to be inconsistent with a continuation of a possible raise gesture;and a preheat determination unit to receive the first and second countervalues from the counter unit and to determine whether a preheat eventhas occurred.

As another example, the gesture detection modules can include a naturaldetection module operable to detect a natural raise gesture. The naturaldetection module can include: a starting pose estimation unit to receivemotion sensor data and to estimate a starting pose based on the motionsensor data; a possible raise gesture determining unit to receive motionsensor data, to determine whether the received data satisfy criteria fora possible raise gesture, and to generate a notification of a possibleraise gesture in the event that the criteria are satisfied; and adetected raise gesture determining unit to receive the notification ofthe possible raise gesture from the possible raise gesture determiningunit, to monitor additional accelerometer data to determine whether acondition is met for a detected raise gesture, and to generate anotification of a detected raise gesture in the event that the conditionis met. In some embodiments, natural detection module can also include acriteria determining unit to determine criteria for detecting a possibleraise gesture based at least in part on the starting pose estimated bythe starting pose estimation unit and to provide the criteria to thepossible raise gesture determining unit. In addition or instead, someembodiments, the natural detection module can also include aconfirmation unit to perform gesture confirmation based on motion sensordata associated with a detected raise gesture and to generate anotification of a confirmed or disconfirmed raise gesture. In someembodiments, the natural detection module can be configured to identifya gesture state from a set of gesture states that includes a null state,a possible raise gesture state, and a detected raise gesture state. Thepossible raise gesture state can be identified, e.g., based at least inpart on a starting pose determined from the motion sensor data and a setof criteria for a change from the starting pose to an ending pose, theset of criteria being selected based at least in part on the startingpose. The detected raise gesture state can be identified, e.g., based atleast in part on a dwell time in a focus pose.

As another example, the gesture detection modules can include alow-dynamic natural detection module operable to detect a natural raisegesture in a low-dynamic environment and a high-dynamic naturaldetection module operable to detect a natural raise gesture in ahigh-dynamic environment.

As another example, the gesture detection modules can include adeliberate detection module operable to detect a deliberate raisegesture. The deliberate detection module can include: a primingdetection unit to receive motion sensor data and to determine from themotion sensor data whether the user's arm is primed to execute adeliberate raise gesture; an impulse peak detection unit to receiveadditional motion sensor data and detect the presence of a target numberof impulse peaks based on the additional motion sensor data; and astability detection unit to receive further motion sensor data anddetermine whether the further motion sensor data indicates that thedevice position has stabilized following detection of the target numberof impulse peaks by the impulse peak detection unit.

As another example, the gesture detection modules can include aloss-of-focus detection module operable to detect a transition of thedevice out of a focus state. The loss-of-focus detection module caninclude: an orientation determining unit to receive motion sensor dataand to determine an orientation for the device based on the motionsensor data; an orientation change detection unit to determine, based atleast in part on the orientation determined by the orientationdetermining unit, whether a change in orientation has occurred; an armposition estimation unit to receive motion sensor data and to determinefrom the data an estimated arm position of an arm on which the device ispresumed to be worn; and a focus determination unit to receiveorientation change information from the orientation change detectionunit, to receive the estimated arm position from the arm positionestimation unit, and to determine, based at least in part on thereceived orientation change information and estimated arm position,whether loss-of-focus has occurred.

In some embodiments, the device can also include an activity classifiermodule operable to determine a current activity of a user based at leastin part on motion sensor data from the motion sensor.

In some embodiments, the device can also include a gesture classifiermodule operable to confirm a raise gesture detected by at least one ofthe gesture detection modules.

Thus, although the invention has been described with respect to specificembodiments, it will be appreciated that the invention is intended tocover all modifications and equivalents within the scope of thefollowing claims.

What is claimed is:
 1. A method executed in a device, the methodcomprising: establishing, in a first processor of the device that thedevice is in a focus state, wherein the focus state includes a userinterface component of the device being in an active state; receiving,by the first processor, a sequence of motion-sensor data samples from amotion sensor of the device; detecting, by the first processor, a changein an orientation of the device based on the motion-sensor data samples;identifying, by the first processor, a loss-of-focus gesture based atleast in part on the change in the orientation; and notifying, by thefirst processor, another component of the device when the loss-of-focusgesture is detected.
 2. The method of claim 1 wherein the change in theorientation includes a change in a tilt angle of the device.
 3. Themethod of claim 1 wherein the motion-sensor data samples includeaccelerometer data samples from an accelerometer.
 4. The method of claim1 wherein the motion-sensor data samples include gyroscope data samplesfrom a gyroscopic sensor.
 5. The method of claim 1 wherein themotion-sensor data samples include accelerometer data samples from anaccelerometer and gyroscope data samples from a gyroscopic sensor, themethod further comprising: selecting, by the first processor, whether touse accelerometer data samples or gyroscope data samples, the selectionbeing based at least in part on a current activity of the user.
 6. Themethod of claim 1 wherein detecting the change in the orientationincludes: determining a reference tilt angle while the device is in thefocus state; and determining a net change in the tilt angle relative tothe reference tilt angle, wherein the change in the orientation includesthe net change in the tilt angle.
 7. The method of claim 1 wherein theloss-of-focus gesture is identified in the event that the change in theorientation exceeds a threshold.
 8. The method of claim 1 wherein theloss-of-focus gesture is identified in the event that the change in theorientation continuously exceeds a threshold for at least a minimumamount of time.
 9. The method of claim 8 further comprising: determininga duration of the focus state, wherein the minimum amount of timeincreases as the duration of the focus state increases.
 10. The methodof claim 1 wherein identifying the loss-of-focus gesture is based inpart on the change in the orientation and in part on a current activityof a user.
 11. The method of claim 10 wherein the current activity ofthe user is determined using an activity classifier.
 12. A devicecomprising: a user interface component having an active state and aninactive state; a motion sensor to detect motion of the device; and afirst processor configured to: establish that the device is in a focusstate, wherein the focus state includes a user interface component ofthe device being in an active state; receive a sequence of motion-sensordata samples from a motion sensor of the device; detect a change in anorientation of the device based on the motion-sensor data samples;identify a loss-of-focus gesture based at least in part on the change inthe orientation; and notify another component of the device when theloss-of-focus gesture is detected.
 13. The device of claim 12 whereinthe device is a wearable device.
 14. The device of claim 12 wherein thedevice is a wrist-wearable device.
 15. The device claim 12 wherein theuser interface component includes one or more of: a display; atouch-screen display; a microphone; a speaker; or a button.
 16. Thedevice of claim 12 wherein the motion sensor includes one or more of: anaccelerometer; or a gyroscopic sensor.
 17. The device of claim 12further comprising an applications processor, wherein the firstprocessor is a coprocessor.
 18. The device of claim 12 wherein the firstprocessor is an applications processor.
 19. A computer-readable storagemedium having stored therein program instructions that, when executed bya first processor in a device, cause the first processor to perform amethod comprising: establishing that the device is in a focus state,wherein the focus state includes a user interface component of thedevice being in an active state; receiving a sequence of motion-sensordata samples from a motion sensor of the device; detecting a change inan orientation of the device based on the motion-sensor data samples;identifying a loss-of-focus gesture based at least in part on the changein the orientation; and notifying another component of the device whenthe loss-of-focus gesture is detected.
 20. The computer-readable storagemedium of claim 19 wherein detecting the change in the orientationincludes: determining a reference tilt angle while the device is in thefocus state; and determining a net change in the tilt angle relative tothe reference tilt angle, wherein the change in the orientation includesthe net change in the tilt angle.